Safety device and method of manufacturing the same

Abstract

A security device is provided comprising a surface relief structure formed from one or more cured materials on a substantially planar substrate, the surface relief structure defining a first set of first-level relief elements of a first scale and a second set of second-level relief elements of a second scale, the second scale being smaller than the first scale, the first set of first-level relief elements comprising a plurality of raised projections, the plurality of raised projections being spaced apart by recesses, and the second set of second-level relief elements being disposed on top of at least one of the raised projections and / or in at least one of the recesses. A security device is also provided comprising a structure and an embossed structure formed from one or more cured materials. Manufacturing methods are also disclosed.

Description

[0001] Cross-references to related applications

[0002] The entire contents of each of the following six international patent applications filed on 10 September 2021 in the name of De La Rue International Limited, claiming priority to the following UK patent applications (all filed on 11 September 2020), are incorporated herein by reference: GB2014325.1, GB2014326.9, GB2014327.7, GB2014328.5, GB2014329.3, GB2014330.1, and GB2014331.9. Technical Field

[0003] This invention relates to security devices, such as those that can be used as markers of authenticity associated with valuables, including security documents such as banknotes, passports, certificates, licenses, etc. A method for manufacturing the security device is also disclosed. Background Technology

[0004] Valuable items, and especially valuable documents such as banknotes, checks, passports, identification documents, certificates, and licenses, are frequently targeted by counterfeiters and those wishing to fraudulently copy and / or alter any data contained within them. Typically, such items are equipped with numerous visible security devices to verify their authenticity. Examples include features based on one or more patterns, such as microtext, fine line patterns, latent images, louvered devices, lenticular devices, moiré interference devices, and moiré magnification devices, each of which produces a reliable visual effect. Other known security devices include holograms, watermarks, embossing, perforation, and the use of color-changing or luminescent / fluorescent inks. What all these devices have in common is that the visual effect produced by the device is extremely difficult or impossible to replicate using available copying techniques such as photocopying. Security devices exhibiting invisible effects, such as magnetic materials, may also be employed.

[0005] A popular security feature found on many known security documents is the printed, tactile macroscopic image, such as a portrait, created through intaglio printing. Intaglio printing is well-suited for creating tactile protrusions on traditional substrates such as paper. For example, many circulating banknotes feature images, such as portraits or architectural drawings, applied through intaglio printing. Typically, all or part of the image is formed by an array of image elements, such as fine lines or dots, which can be individually discerned under close examination and / or magnification. Intaglio printing not only ensures high resolution and accurate reproduction of images (which prevents the production of qualified counterfeits through readily available commercial printing techniques), but it can also be used to impart a tactile feel to the image. This significantly enhances the level of security because potential counterfeiters can use highly precise printing systems that can reproduce the visual appearance of intaglio printing but not its three-dimensional quality, and therefore its tactile feel. However, the tactile feel provided by intaglio printing is limited by the amount of ink that can be transferred to the substrate and the amount of thermal / stress deformation that the substrate can withstand / retain. Specifically, polymer banknotes have poor thermal stability and cannot be indented like paper. This results in a lower intaglio profile. Therefore, it is desirable to provide security features that overcome these shortcomings. Summary of the Invention

[0006] According to a first aspect of the invention, a safety device is provided, comprising: a surface relief structure formed by one or more curing materials on a substantially flat substrate, the surface relief structure defining a first-level relief element set at a first dimension and a second-level relief element set at a second dimension smaller than the first dimension, the first-level relief element set including a plurality of raised protrusions spaced apart by recesses, and the second-level relief element set disposed on top of at least one of the raised protrusions and / or disposed in at least one of the recesses.

[0007] The safety device according to the invention utilizes a surface relief structure formed from one or more curable materials, which is formed on a substantially flat substrate. In other words, the relief elements of the surface relief structure in the invention are not formed by gravure printing, where the substrate exhibits locally raised areas due to the imprinting process. The surface relief structure of the invention is preferably formed by a casting process such as casting-curing. Thus, the casting-curing structure can be used instead of gravure. For example, the gravure grooves used in standard gravure printing can be used for casting imprinting, where the height and width are variable according to the standard gravure. In other words, relief elements typically produced by grooves in a gravure printing plate can be formed by casting-curing one or more suitable materials in a surface relief mold having recesses corresponding to the shape and arrangement of the gravure grooves.

[0008] This method, using a surface embossed structure formed from one or more curing materials, offers numerous advantages over standard gravure printing. For example, casting-curing can be performed at low temperatures and low pressures (compared to standard gravure printing). This means the process is more compatible with the substrate, as it does not deform the substrate. In other words, the surface embossed structure is formed on a substantially flat substrate, as detailed above (i.e., a substantially flat substrate does not exhibit the localized raised areas that would be present after a conventional embossing process). This makes downstream processing of the casting process easier. For example, deforming the substrate via standard gravure printing often makes registration in subsequent printing processes more difficult to manage (a problem known as "flowering"). With this technique, the embossed elements of the cured material are set on a substantially flat substrate, which increases the ease with which subsequent printing processes can be performed accurately and repeatedly, resulting in improved registration between different parts of a security device or security document.

[0009] Because this invention utilizes one or more curing materials, contamination (the undesirable transfer of ink from one printing sheet to another) can be avoided—a common problem in the production of gravure inks on paper and polymers. Furthermore, gravure inks have long drying times, and this drawback of conventional gravure printing is overcome by using curing materials in this method, as the curing of the embossed surface structure occurs essentially instantaneously.

[0010] Furthermore, compared to gravure printing, where the reproduction of the structure is limited by the amount of ink that can be transferred from the gravure plate / rubber blanket to the substrate, the use of one or more curing materials means that the surface relief structure of the present invention more faithfully replicates the desired imprint. In this way, the present invention allows for greater design flexibility and more tactile structures compared to conventional gravure printing, thereby improving the safety level of the device. Casting-curing allows for substantially accurate replication of the imprinted surface relief structure.

[0011] The use of conventional gravure printing with optically variable (e.g., holographic) foil (especially foil in polymer configurations) is limited due to the offsetting effect and potential damage caused by the gravure printing plate / blanket. Therefore, this invention is more compatible with additional safety devices, especially with vulnerable components such as holographic foil, compared to standard gravure printing.

[0012] Furthermore, the degradation of the surface relief structure formed on the cured material will be less than that of features formed by gravure. Therefore, compared to gravure, the safety device according to the invention maintains its safety level over an extended period of time.

[0013] Therefore, the present invention overcomes many known problems of gravure printing.

[0014] The surface relief structure defines a first-level relief element set at a first scale and a second-level relief element set at a second scale, the second scale being smaller than the first scale. For example, the second-level relief element set may define multiple peaks and recesses (e.g., multiple individual elements or as a continuous structure) on a single protrusion or within a single recess of the first-level relief element set. The second-level relief element set is disposed on the top of at least one (preferably at least some, more preferably each) of the protrusions and / or in at least one (preferably at least some, more preferably each) of the recesses. In one embodiment, the second-level relief element set is disposed on the top of at least some of the protrusions and / or in at least some of the recesses. In other embodiments, the second-level relief element set is disposed on the top of each of the protrusions and / or in each of the recesses.

[0015] In a preferred embodiment, a set of second-level embossed elements can be used to control the tactile feel of the surface embossed structure. Therefore, preferably, the set of second-level embossed elements defines one or more tactile structures. The tactile level (e.g., roughness or smoothness) of the tactile structure is typically configured to vary across the entire surface embossed structure. For example, the tactile level can be configured to vary based on the image presented by the embossed elements of the surface embossed structure (e.g., by the first-level embossed elements). The ability to control the perceived tactile feel (e.g., roughness or smoothness) of the cured surface embossed structure across its entire domain provides a very secure means that is difficult or even impossible to produce using standard gravure printing plates due to limitations in ink transfer from the gravure plate to the substrate. The tactile structure is preferably defined by a plurality of individual second-level embossed elements (e.g., an array thereof). In other embodiments, specific (e.g., individual) second-level embossed elements can define the tactile structure by presenting a continuous embossing of peaks and depressions at a scale smaller than the first scale.

[0016] The level of tactile sensation can be configured to vary across the entire surface relief structure in a variety of different ways. In some embodiments, the top of the raised protrusion in the first region has a different (e.g., higher or lower) level of tactile sensation than the top of the raised protrusion in the second region of the device. In other words, the second set of embossed elements defining the tactile structure is preferably disposed at least on the top of the raised protrusion, wherein the tactile structure is configured to provide different levels of tactile sensation across the entire surface relief structure. In this document, "top" is used to refer to the portion of the raised protrusion furthest from the substrate, regardless of the device orientation. Such devices can be formed using a surface relief mold, wherein each "groove" or recess in the surface relief mold has a substructure at its base, the scale of which is within the scale of the individual elements (grooves). This can be a unique tactile substructure. Due to the nature of the casting-curing process, this substructure will be precisely replicated on the top of the embossed elements cast from the mold, a process impossible in gravure. Therefore, the degree of tactile sensation can be controlled and can be configured to vary across different elements within the surface relief structure.

[0017] Alternatively or additionally, the recesses between the protrusions in the first region of the device may have a different (e.g., higher or lower) level of tactile sensation than the recesses between the protrusions in the second region of the device. For example, the spaces between grooves in a mold may have a unique structure—e.g., an ultra-smooth surface. These spaces will ultimately correspond to the recesses between the protrusions in the cast surface relief structure (e.g., regions of lower height). A substructure can be provided here to control the tactile sensation, and due to the nature of the casting-curing process, it will be precisely replicated in the casting material.

[0018] In some embodiments, both the top of the protrusion and the recess between the protrusions include tactile structures. The tactile structure on the top of the protrusion may have a different (e.g., higher or lower) level of tactile sensation than the tactile structure in the recess between the protrusions.

[0019] Typically, the tactile structure defines the tactile level based on at least one of the size, shape, orientation, and / or spacing of the secondary embossed element set. For example, the tactile level of the tactile structure may depend on at least one of the size, shape, orientation, and / or spacing of the secondary embossed element set constituting the tactile structure. Secondary embossed elements with relatively small size and spacing (defining a “relatively fine” arrangement of secondary embossed elements) generally produce a relatively low (e.g., “smooth”) tactile level, while secondary embossed elements with relatively large size and spacing (defining a “relatively rough” arrangement) generally produce a relatively high (e.g., “rough”) tactile level. The orientation of the secondary embossed element set may also affect the tactile level, depending on the direction in which the user’s finger travels on the surface embossed structure.

[0020] The use of a surface relief structure formed from one or more curing materials (e.g., via casting-curing) in this invention advantageously allows for control over the set of secondary relief elements and enhances design freedom to provide the desired tactile effect. In some embodiments, the size, shape, orientation, and / or spacing of the secondary relief elements are substantially uniform in at least one region of the surface relief structure (preferably all regions where the secondary relief elements are present). For example, this could be a periodic arrangement of the secondary relief elements. Such an arrangement of the secondary relief elements provides a consistent tactile feel throughout the corresponding tactile structure (in a particular direction). Alternatively or additionally, the secondary relief elements may have a non-periodic (e.g., random) arrangement in at least one region of the surface relief structure (preferably all regions where the secondary relief elements are present). This can provide further tactile effects.

[0021] In a particularly preferred embodiment, the tactile structures have an asymmetrical arrangement in at least one region of the surface relief structure (preferably all regions in which the tactile structures are present), thereby differentiating the tactile level in a first direction (e.g., across the entire tactile structure) from the tactile level in a second direction (e.g., across the entire tactile structure). The first and second directions are preferably perpendicular to each other. The asymmetrical arrangement of the tactile structures may result from an asymmetrical arrangement of the set of second-level relief elements, or it may be generated by the asymmetrical contours of specific (e.g., continuous) second-level relief elements defining the tactile structure. This arrangement will advantageously provide different sensations depending on the direction in which the user's fingertips move across the surface relief structure. For example, when a user moves their fingertips across the structure in one direction, the structure may feel relatively smooth, while when moving their fingertips in the opposite or perpendicular direction, the structure may feel relatively rough. The tactile structure may provide this asymmetrical arrangement in at least one aspect of the size, shape, orientation, and / or spacing of the set of second-level relief elements, thereby differentiating the tactile level in the first direction from the tactile level in the second direction. The ability to control the parameters of the second-level relief element set in this way advantageously increases the complexity of the device, thereby increasing the difficulty of forgery.

[0022] Typically, the secondary embossed element set can have virtually any geometry to provide the desired tactile effect. This is a particular advantage of using cast-and-cured materials, as the shape of the surface embossed structure will precisely replicate the surface embossing of the mold. In a preferred embodiment, the secondary embossed element set is in the form of at least one of the following: a faceted structure, such as (e.g., linear) a prism (e.g., with a symmetrical or asymmetrical cross-section), a cubic structure, a cone, a pyramidal structure; a curved structure; an irregular structure. In some embodiments, the secondary embossed element set may include additional substructures smaller than the secondary embossed element set, providing further control over the tactile sensation.

[0023] Preferably, the second-level relief element set has a size that makes them indistinguishable to the naked eye. At a typical viewing distance of the device (e.g., 30 cm), the naked eye typically cannot distinguish distances smaller than 100 μm. Therefore, the second-level relief element set typically has a size smaller than 100 μm, making them difficult to distinguish with the naked eye.

[0024] Typically, the protrusion height of the second-level relief element set (e.g., corresponding to the depth of the casting tool recess used to form each element) is between 2 μm and 75 μm. Preferably, the protrusion height of the second-level relief element set is between 2 μm and 25 μm. More preferably, the protrusion height of the second-level relief element set is between 2 μm and 10 μm. Preferably, the width of the second-level relief element set is between 2 μm and 75 μm. More preferably, the width of the second-level relief element set is between 2 μm and 25 μm. More preferably, the width of the second-level relief element set is between 2 μm and 10 μm.

[0025] So far, we have considered the case where a second-level embossed element set defines the tactile structure. Alternatively or additionally, the second-level embossed structure set can define optical elements, preferably faceted elements (e.g., an array of faceted elements), such as prisms or mirrors; focusing elements, such as lenses or focusing lenses; or caustic structures. These devices can provide further optical effects. Such optical elements can be disposed on top of at least one of the raised protrusions and / or in at least one of the recesses between the raised protrusions. Such optical elements are typically located on top of a decorative layer or decorative mark (described in more detail below), whereby the optical elements and the decorative layer / marker cooperate to present optically variable effects. For example, the decorative layer can define a micro-image array and the optical elements can be in the form of a lens array, whereby the micro-image array and the lens array cooperate to present lenticular or moiré optically variable effects. The optical elements are typically refractive optical elements (e.g., focusing lenses), in which case one or more cured materials are preferably at least partially transparent (e.g., transparent to visible light), but can be in the form of reflective optical elements (e.g., focusing lenses).

[0026] A second-level set of relief elements is envisioned that can define tactile structures and optical elements, such that the surface relief structure includes a combination of tactile and optical structures.

[0027] As discussed above, surface relief structures are typically formed using a casting-curing technique. Therefore, the recesses (e.g., one or more) between the raised protrusions typically comprise a base layer of one or more cured materials, whereby the multiple raised protrusions of the first-level relief element set are connected by the base layer, which has a lower height than the raised protrusions of the first-level relief element set. In other words, each surface relief structure will comprise a continuum of cured material with a varying height profile between the base layer and the relief element. This is not the case in devices with tactile protrusions formed by partial printing materials (e.g., conventional gravure), and thus represent fundamentally different structures. This continuous nature of the surface relief structure needs to be considered in the design of security devices so that it presents the desired optical effects, especially when the casting-curing resin is stained or colored.

[0028] The thickness of the base layer is typically between 0.5 μm and 1 μm. Preferably, the ratio of the height of at least one protrusion to the height of the base layer connecting the protrusion to the adjacent protrusion is at least 20, and more preferably no more than 400, and more preferably no more than 200. In some embodiments, the ratio of the height of each protrusion element to the height of the base layer is at least 20, and more preferably no more than 400, and more preferably no more than 200. This is especially true when the protrusions are configured to form image elements, particularly image elements of multi-tone images (such examples are further described herein).

[0029] In some embodiments, the base layer may extend over a peripheral region surrounding the raised protrusions. This peripheral region of the base layer may be narrow in some cases, for example, extending 0.01 mm to 5 mm from the multiple raised protrusions. This may be the case, for example, if the device is positioned within a window area of ​​a security document substrate defined by the absence of a partially opaque layer. In other examples, the surface embossed structure including the peripheral region of the base layer may extend over a wider area, for example, to serve as a protective layer over the entire security document substrate or its entire area. In such examples, the surface embossed structure may extend beyond at least 5%, preferably at least 10%, and even more preferably at least 50% of such a security document substrate. A preferred range is 10% to 60%. The surface embossed structure including the peripheral region of the base layer may serve as a protective layer (similar to a paint layer) over substantially the entire document substrate, in which case the surface embossed structure may extend beyond at least 75% (including 100%) of the document substrate.

[0030] Optionally, the height (or “thickness”) of the base layer can vary across the entire surface embossed structure. The height of the base layer can vary discretely (e.g., in the form of a “stepped variation” where the height varies over a substantially zero lateral dimension) and / or continuously, for example, to define a sloping portion of the base layer. The additional complexity that can be added to the surface embossed structure by varying the height of the base layer is not typically achievable using conventional gravure printing, thus further enhancing the security level of the device disclosed in this invention. For example, varying the height of the base layer can allow the tactile structure positioned on top of the raised protrusion to be at different relative heights above the substrate. As another advantage, the height of the base layer can be used to compensate for thickness variations across the entire security document.

[0031] As discussed, the second-level embossed element set can have varying parameters to control the tactile and / or optical properties presented by the device. In some embodiments, the height and / or width of the raised protrusions of the first-level embossed element set vary across the entire surface embossed structure. This can provide additional tactile and / or optical effects. For example, in embodiments where the second-level embossed element set defines the tactile structure, varying the height of the raised protrusions allows the tactile structure positioned on top of the raised protrusions to be located at different relative heights above the substrate, providing further variation and design freedom for the overall tactile level of the device. Variation in the height and / or width of the raised protrusions also allows for further control over the tactile level of the entire surface embossed structure. The height of the raised protrusions can vary within each raised protrusion and / or across different raised protrusions (i.e., one raised element has a different height than another raised element).

[0032] The raised protrusions are typically large enough to be individually identifiable under close inspection (e.g., using magnifying aids). Typical lateral dimensions of the raised protrusions (e.g., corresponding to the linewidth of a line element) range from 20 μm to 8 mm (e.g., the upper limit used for woodblock printing), more preferably from 30 μm to 3 mm, even more preferably from 30 μm to 1 mm, and even more preferably from 50 μm to 500 μm. Typical spacing between the raised protrusions is greater than 30 μm. Preferred heights of the raised protrusions range from 20 μm to 200 μm, preferably from 20 μm to 150 μm, more preferably from 20 μm to 100 μm, and even more preferably from 20 μm to 50 μm. Due to the nature of the casting-curing process used to form the surface relief structure, these preferred dimensions can be achieved on both paper and polymer substrates, providing further advantages over conventional gravure processes where dimensions are typically dependent on the substrate.

[0033] In a preferred embodiment, the multiple raised protrusions of the first-level relief element set correspond to elements of an image, preferably a halftone image. In such embodiments, the raised protrusions of the first-level relief element set may be referred to as raised elements. For example, raised elements may define dotted screens of line art (e.g., similar to conventional line intaglio images) or image elements, such as halftone screens. The elements may be (e.g., straight or curved) line elements, dotted elements, or defining markers such as letters, numbers, currency symbols (e.g., £, $, etc.). The image may include a guilloche pattern. Desiredly, the image is a portrait or architectural drawing. Preferably, the image is an image of a 3D object or scene. In embodiments where the image is a halftone image, the elements of the image are preferably arranged on a regular grid, although typically elements may or may not be arranged on a regular grid. Preferably, the size, shape, orientation, spacing, and / or color density of the raised protrusions (raised elements) vary across the entire surface relief structure to present a multi-tone variation of the image. In this way, the image presented by the device can reproduce a traditional intaglio image very closely. However, the raised elements can be in the form of a regular array that does not exhibit tonal variations. At least one of the raised elements can be in the form of a continuous or "woodcut" print of elements defining the image.

[0034] In embodiments where the second-level set of embossed elements defines the tactile structure, these can advantageously provide additional tactile feedback to the image. In a particularly preferred embodiment, the second-level set of embossed elements defines the tactile structure, and wherein the tactile level of the tactile structure is configured to vary across the entire surface embossed structure according to the image. This provides additional safety features, advantageously further enhancing the safety level of the device. For example, the tactile structure can be configured such that specific areas of the image exhibit a rough tactile feel, while different areas of the image exhibit a finer tactile feel.

[0035] In some preferred embodiments, the second-level set of embossed elements defines a tactile structure, and the device includes a first region and a second region, both presenting substantially the same image, but with different tactile levels of the tactile structures in the first and second regions. Preferably, the tactile levels of the tactile structures in the first and second regions differ along a first direction. In an alternative embodiment, the second-level set of embossed elements defines a tactile structure, and the device includes a first region and a second region, both presenting different (preferably related) images, but with substantially the same tactile structure. In such embodiments, the relationship between visual and tactile effects in different regions of the device allows for a particularly safe device. Different regions may constitute different surface embossed structures, or different regions may constitute the same surface embossed structure.

[0036] In some embodiments, the multiple raised protrusions include raised platforms, and wherein the second-level embossed element set is at least partially located on the raised platforms. This embodiment may be particularly preferred when the second-level embossed element set defines an optical element such as a lens; for example, a lens array may be disposed on top of the platform, wherein the height of the raised platform is such that the decorative layer designed to cooperate with the lens is substantially within the focal plane of the lens.

[0037] In some embodiments, the tops of the raised protrusions and / or the tops of the set of second-level embossed elements have a substantially constant height over at least a portion (preferably, all) of the surface embossed structure. For example, in embodiments where the second-level embossed elements are disposed only in recesses between the plurality of raised protrusions, the height of each second-level element can be such that the tops of the second-level elements and the tops of the raised protrusions are substantially at the same height over the entire surface embossed structure (e.g., relative to the substrate). In some arrangements, tactile structures can be disposed on the tops of the raised protrusions and in recesses between the raised protrusions, and the height of each second-level element varies according to the height of the raised protrusions such that the tops of the second-level embossed elements have a substantially uniform height above the substrate.

[0038] This implementation, which presents a variation in tactile feel due to the variation in the height of the individual second-level embossed elements and / or raised protrusions, can advantageously compensate for thickness variations across the entire security document caused by the substantially uniform height of the tops of the raised protrusions and / or the tops of the second-level embossed element set (e.g., relative to the substrate). For example, this can advantageously improve the ream shape and handling performance in downstream processes.

[0039] One or more cured materials for the surface relief structure may be transparent and colorless (under standard white light), which may be desirable to provide tactile features that are only partially visible due to their surface reflection. Alternatively, one or more cured materials may have a color that is visible to the naked eye under at least some observation conditions (preferably white light illumination, but alternatively under special illumination such as UV).

[0040] Preferably, one or more curing materials are at least translucent. As emphasized above, in embodiments where the base layer extends between the protrusions, the continuous nature of the surface relief structure needs to be considered in the design of the safety device so that it presents the desired optical effects (such as multi-tone or multi-color images). Here, it is desirable to use at least translucent curing materials so that the base layer has a low optical density. However, substantially opaque surface relief structures are also contemplated. At least one curing material can be transparent and colorless. In embodiments, at least one curing material preferably includes a visible colorant. Typically, at least one curing material has a base color of at least one color, i.e., the curing material is at least translucent while having a color visible under at least some observation conditions. Such embodiments are particularly advantageous for presenting multi-tone images because variations in the surface relief structure (e.g., variations in the size, shape, orientation, spacing, and / or color density of the protrusions corresponding to elements of the image) mean that the perceived color intensity varies throughout the surface relief structure.

[0041] In some embodiments, at least one cured material includes a machine-readable substance. Examples of suitable machine-readable substances (e.g., substances that respond to external stimuli) include any luminescent, fluorescent, or phosphorescent material, or a material that exhibits Raman scattering. Magnetic materials may be used. In this way, the surface embossed structure of the device can be detected by a detector configured to detect the machine-readable substance (“labeling agent”). Typically, the desired external stimulus and / or the emission of the machine-readable substance is outside the visible range of the electromagnetic spectrum (typically in the infrared, IR, or ultraviolet, UV range), such that the machine-readable substance is not detectable under standard visible light conditions. This advantageously increases the security level of the device because a potential counterfeiter would need not only to replicate the tactile sensation presented by the surface embossed structure but also to replicate the machine-readable emission. Furthermore, the detection signal varies depending on the amount of labeling agent present. Preferably, the amount of machine-readable substance present in each region of the surface embossed structure varies according to the height of that region relative to the substrate (e.g., the thickness of the cured material in that region), thereby causing the detection signal to vary similarly according to the height of the surface embossed structure. This can generate machine-readable codes. This variation in the detection signal, corresponding to the height of the surface relief structure, further enhances the safety level. Furthermore, this allows for improved quality control during device manufacturing, as the detection signal from the machine-readable material can be analyzed to assess the quality of the structure (and the determination of its presence). In embodiments where the curable material includes machine-readable material, the amount of machine-readable material present (e.g., depending on both the particle size and concentration of the labeling agent) is preferably low enough to make the curable material optically transparent. It has been found that it is preferable to have a haze value (e.g., transmission) of less than 50%, preferably less than 30%, more preferably less than 10%; and / or an optical density value of less than 0.3, preferably less than 0.15, more preferably less than 0.05.

[0042] In some embodiments, the device further includes a decorative layer formed on a first and / or second surface of a substrate, wherein the surface relief structure is at least partially superimposed on the decorative layer, such that the decorative layer and the surface relief structure can be observed in combination under at least some viewing conditions. Therefore, at least from one viewing angle, an observer of the device will perceive the combined effect of the decorative layer (or multiple decorative layers) and the surface relief structure, wherein the surface relief structure is positioned between the decorative layer and the observer, or the decorative layer is positioned between the surface relief structure and the observer. This allows the device to present more complex effects, thereby further enhancing its security level.

[0043] Decorative layers may include one or more of the following: a printed layer; an optically variable layer, such as a color-shifting layer or a diffraction structure; and a reflective (e.g., metallic) layer. When the decorative layer includes a printed layer, this is preferably in the form of a lithographic print. For example, a surface embossed structure can be provided on a lithographic print as part of a conventional banknote manufacturing process. However, such a printed layer can be provided by other printing techniques such as gravure printing, offset printing, flexographic printing, inkjet printing, or other convenient methods. These printing techniques can be described as providing “flat” prints, i.e., they do not include multiple raised elements.

[0044] Decorative layers can include optically variable layers, such as color-shifting layers or diffractive foils. These are examples of vulnerable features that are generally difficult or impossible to combine with standard gravure articles because the temperature and pressure involved in conventional gravure processes typically damage such features. However, this technique, which uses curing materials (e.g., via casting curing) instead of imprinting, advantageously allows for the combination of such optically variable features with surface relief structures. The term "optically variable effect" refers to an optical effect that changes with the viewing angle, for example, when the device is tilted. Examples of color-shifting layers include layers combining liquid crystals (e.g., liquid crystal films), interference pigments (including magnetically oriented interference pigments), pearlescent pigments, structured interference materials (including dielectrics and Fabry-Perot structures), photonic crystals, or thin-film interference structures (including Bragg stacks). Diffractive structures can be in the form of diffractive optically variable imaging devices ("DOVIDs"), such as holographic foils or cast-cured holograms (e.g., with an accompanying metallic or high-refractive-index layer). Other examples include nanodiffractive structures and plasmons, as well as other sub-wavelength structures.

[0045] Decorative layers may include (e.g., printed) plasma inks or metallic inks.

[0046] In particular, in embodiments where the safety device includes a decorative layer, the present invention also provides multiple substantially identical safety devices, each as described above, wherein the corresponding surface embossing structure and decorative layer have the same position relative to each other. This is due to the precise alignment of the two components during manufacturing. The term "same position" means that the amount of variation in the relative position of the corresponding surface embossing structure and printed layer is less than a visually detectable amount between the safety devices, if any. For example, the translational variation in the machine direction or lateral direction may be + / - 75 μm or less. The skew variation is preferably 1 degree or less, more preferably 0.1 degree or less, still preferably 0.05 degree or less, and most preferably 0.02 degree or less. Multiple safety devices will typically be produced sequentially on the same production line and according to the same design—for example, multiple safety devices may comprise a whole batch of safety devices, or the whole of a print run. Multiple safety devices may comprise at least 10 safety devices, more preferably at least 100 safety devices. Each of the multiple safety devices may ultimately be located on a different safety document. Most preferably, the formation of the surface relief structure and the formation (e.g., printing) of the decorative layer (e.g., a printed layer) are simultaneous, occurring at the same location along the machine direction. This achieves the highest level of registration between the two components of the safety device, because no slippage or deformation of the substrate occurs after one step and before the next (since there is no interval between the two steps). Suitable apparatus for simultaneously casting-curing and printing on opposite sides of a substrate is disclosed in WO-A-2018 / 153840 and WO-A-2017 / 009616. The level of registration that can be provided by simultaneous casting and printing using the apparatus disclosed therein cannot be achieved on a rotary printing press or in two separate processes.

[0047] According to a second aspect of the invention, a safety device is provided, comprising: a surface relief structure formed on a substrate by one or more curable materials; and an embossed structure on or adjacent to one or more curable materials on the substrate. Thus, the safety device according to the second aspect of the invention can advantageously include cast-cured elements and elements formed by conventional gravure printing. Preferably, the surface relief structure formed by one or more curable materials is applied first (e.g., by cast curing), and then the embossed structure is applied, but this can be reversed.

[0048] The embossed structure can be adjacent to the cured surface relief structure. This can advantageously create a contrast between two tactile areas that can be achieved from two processes. The tactile contrast will be particularly pronounced if the casting-curing area and the embossed area are adjacent to each other (preferably adjacent).

[0049] The embossed structure can be disposed on one or more cured materials on a substrate. For example, in one embodiment, a surface relief structure formed of one or more cured materials defines a plurality of raised protrusions spaced apart by recesses, and the raised portions of the embossed structure are located in at least one (preferably at least some, more preferably each) of the recesses and / or on at least one (preferably at least some, more preferably each) of the raised protrusions. This provides a more complex tactile effect in addition to the effect generated by one or more cured materials. Typically, the recesses between the raised protrusions of the surface relief structure comprise a base layer of the one or more cured materials or another one or more cured materials, which preferably has a lower height than the raised protrusions of the surface relief structure. Therefore, the raised portions of the embossed portion can be located on the recessed areas of the base layer.

[0050] In some embodiments, a surface relief structure formed of one or more curable materials defines at least one platform that is higher than the adjacent area, and the raised portion of the embossing structure is located on the platform and / or on the adjacent area. Typically, the adjacent area is the base layer region of the surface relief structure. Positioning the embossed portion on such a platform formed of one or more curable materials can advantageously improve the height range of the embossed (e.g., gravure) article compared to standard gravure printing, particularly on polymer substrates. Such embodiments are particularly advantageous because the raised platform allows for the formation of gravure articles of varying heights using a single gravure printing plate.

[0051] Flexible curable materials can be used in cast-cured components to provide them with additional elasticity, thereby helping to withstand embossing (e.g., gravure) processes, but this is not necessary.

[0052] In a preferred embodiment, the raised portion of the embossed structure includes one or more inks. The ink can be a colored ink, for example, having the same or different color as one or more curing materials of the surface relief structure. However, generally, the embossed structure can be inked or uninked (i.e., "blind" embossing).

[0053] Preferably, the embossed structure is formed by gravure printing. The raised portions of the embossed structure may correspond to elements of an image, preferably a halftone image. This image may be a multi-tone and / or multi-color image. Typically, the raised protrusions of the cast surface relief structure correspond to (e.g., halftone) elements of an image. The raised portions of the embossed structure and / or the raised protrusions of the cast surface relief structure may vary in at least one aspect of size, shape, orientation, spacing, and color density to present a multi-tone image. In embodiments, both the cast surface relief structure and the embossed structure present images that may complement each other or be components of the same common image.

[0054] In some embodiments of the second aspect, a surface relief structure formed of one or more curable materials defines a first-level set of relief elements at a first scale and a second-level set of relief elements at a second scale, the second scale being smaller than the first scale. The first-level set of relief elements includes a plurality of raised protrusions spaced apart by recesses, and the second-level set of relief elements is disposed on top of at least one (preferably at least some, more preferably each) of the raised protrusions and / or disposed in at least one (preferably at least some, more preferably each) of the recesses. Preferably, the second-level set of relief elements defines a tactile structure as described herein. In a preferred embodiment, the tactile level of the tactile structure is configured to vary across the entire surface relief structure according to an image rendered by the surface relief structure and / or embossed structure. In other embodiments, the second-level set of relief elements may define optical elements.

[0055] In an embodiment of the second aspect of the invention, the surface relief structure formed on the substrate by one or more curing materials can be the surface relief structure defined in any embodiment discussed in the first aspect of the invention.

[0056] A safety device is also disclosed, comprising: a surface relief structure formed by one or more cured materials on a substantially flat substrate, the surface relief structure following the contour of a three-dimensional image, preferably a portrait. Further preferred features in this regard include:

[0057] • Depth control during casting and curing allows for better 3D tactile representation – pseudo-embossing.

[0058] • Generate a full 3D haptic structure—that is, a contour map of a mountain range or facial outline.

[0059] Typically, the substrate may include paper, polymers (e.g., biaxially oriented polypropylene, BOPP, or polycarbonate), cellulose, or combinations thereof. Preferably, the substrate is a polymer substrate, optionally provided with one or more opaque layers.

[0060] According to a third aspect of the invention, a security document is provided, comprising a document substrate and a security device on the document substrate, the security device being a security device according to any of the examples described above, wherein the document substrate may or may not be used as a substrate for the security device, and the document substrate preferably comprises paper, polymer, cellulose, or a mixture thereof. It should be understood that the security document may therefore comprise a single substrate that serves both as a document substrate (i.e., a self-supporting sheet forming the body of the document) and as a security device substrate (i.e., a substrate with a surface embossed structure).

[0061] In a preferred embodiment, the security device is at least partially located in a window area or half-window area of ​​the document substrate, which has a lower light density compared to its surrounding area. The window area may be a half-window area, in which case the optical effect of the security device (e.g., the raised protrusions of a first-order embossed element set corresponding to elements of an image) can be observed in either reflection or transmission if the opacity of the opaque side of the half-window is low enough to allow light to pass through. The window may be a full window, in which case the device is intended for observation in transmission. In some embodiments, the security device may be at least partially located in a non-window area of ​​the document substrate, which may be opaque, and the device is generally intended for observation in reflection.

[0062] In a preferred example, the document substrate comprises a core polymer substrate having at least one opaque layer disposed on one or both surfaces of the core polymer substrate, with optional gaps in one or more of the opaque layers forming window or semi-window areas of the document substrate. For example, a security document could be a polymer banknote. The opaque layer is preferably a non-fibrous material, such as a coating of adhesive containing light-scattering pigments, and preferably white, off-white, or gray (such as TiO2).

[0063] In some embodiments, the document substrate also includes an integral decorative mark, which is preferably at least partially superimposed on the surface embossed structure. The “decorative mark” (distinct from the decorative layer described above) is incorporated into the substrate during substrate production, not during its later processing into a secure document. For example, the decorative mark may be applied during the same process used to apply the opaque layer (e.g., gravure printing). The decorative mark is integral with the document substrate. The integral decorative mark may be independent of currently disclosed security devices. However, preferably, the integral decorative mark is at least partially superimposed on the surface embossed structure (and / or, in embodiments where the device includes adjacent curing and embossing structures), such that the decorative mark and the surface embossed structure can be viewed in combination under at least some viewing conditions. For example, the decorative mark and the surface embossed structure may both define the same image and may be arranged in an aligned superimposed configuration (e.g., overlay). The decorative mark may be a watermark in the paper substrate.

[0064] Although decorative markings typically feature colors visible under white light, they may also have colors visible under special lighting conditions such as IR or UV. While integral decorative markings are typically in the form of printed articles (printed markings) as described above, decorative markings may include or incorporate other elements or components, such as optically variable parts (e.g., color shift layers or holographic foils), or, referring to embodiments including decorative layers, decorative markings may include or incorporate reflective / metallic parts as described above.

[0065] Where the security device is not directly formed on the document substrate, the security device substrate can be fixed to or bonded to the document substrate. Preferably, the security device substrate can be fixed to or bonded to a transparent or semi-transparent area of ​​the document substrate, which may optionally be formed as an aperture. However, it is contemplated that the device can be fixed to the document substrate over a non-transparent area (e.g., over an opaque layer area), in which case the device is designed to be observed in reflection.

[0066] Preferably, the security document is any one of the following: banknotes, passport, identity document, ID card, bank card, driver's license, visa, stamp, check or certificate.

[0067] According to a fourth aspect of the present invention, a method for manufacturing a safety device is provided, the method comprising: forming a surface relief structure on a substrate using one or more curable materials and curing the one or more materials, wherein the surface relief structure is formed by: providing a casting tool having a relief structure defined in the surface of the casting tool, the relief structure corresponding to the surface relief structure; applying one or more curable materials to the substrate and / or to the relief structure of the casting tool; bringing the substrate and the casting tool together to form one or more curable materials according to the relief structure, and curing the one or more materials... One or more curable materials are cured such that a surface relief structure formed by one or more cured materials is retained on a substrate; wherein the surface relief structure defines a first-level relief element set at a first scale and a second-level relief element set at a second scale, the second scale being smaller than the first scale, the first-level relief element set including a plurality of raised protrusions spaced apart by recesses, and the second-level relief element set being disposed on the top of at least one (preferably at least some, more preferably each) of the raised protrusions and / or disposed in at least one (preferably at least some, more preferably each) of the recesses.

[0068] This is a casting-curing process. The curing mode will depend on the type of curable material used. In a preferred example, the material is radiation-curable (e.g., UV-curable) and one or more curing steps will involve irradiating the material with radiation of a suitable wavelength to induce cross-linking. Curing of one or more curable materials can occur during and / or after bringing the substrate and casting tool together. One or more curable materials are typically applied to the substrate, or alternatively, to the embossed structure of the casting tool. However, in some embodiments, curable materials can be applied to a combination of both the substrate and the casting tool, particularly if more than one curable material is used. Because the casting-curing process does not have the same pressure / thermal constraints as gravure printing, surface embossed structures can be formed at virtually any stage of the manufacturing process of security devices or security documents, increasing workflow flexibility. For example, surface embossed structures can be applied before or after conventional lithographic printing or foil application during banknote manufacturing processes.

[0069] Therefore, the method provides an apparatus that exhibits all the advantages summarized above with respect to the first aspect of the invention.

[0070] Preferably, the relief structure of the casting tool includes a plurality of grooves spaced apart by raised regions, these grooves corresponding to a first-level relief element set, and wherein at least one (preferably at least some, more preferably each) of these grooves has a base portion and / or at least one (preferably at least some, more preferably each) of the raised regions (e.g., spaces) between these grooves is provided with a substructure corresponding to a second-level relief element set. As previously described, the second-level relief element set preferably defines a tactile structure such that the substructure of the casting tool forms a tactile structure within the surface relief structure of the casting. Alternatively, the substructure of the casting tool can be used to form optical elements, such as prisms, mirrors, or focusing elements, as described above.

[0071] According to a fifth aspect of the invention, a method of manufacturing a safety device is provided, the method comprising: a) forming a surface relief structure on a substrate from one or more curable materials and curing one or more materials, wherein the surface relief structure is formed by: a1) providing a casting tool having a relief structure defined in the surface of the casting tool, the relief structure corresponding to the surface relief structure; a2) applying the one or more curable materials to the substrate and / or to the relief structure of the casting tool; a3) bringing the substrate and the casting tool together to form one or more curable materials according to the relief structure, and curing one or more curable materials such that the surface relief structure formed by the one or more curable materials is retained on the substrate; and b) performing gravure printing on the substrate to form an inked or uninked embossed portion on the substrate, the embossed portion being located on or adjacent to the surface relief structure.

[0072] Therefore, the method provides an apparatus that exhibits all the advantages summarized above with respect to the second aspect of the invention.

[0073] In the casting curing process described in the fourth and fifth aspects of the present invention above, one or more curable materials are applied to a substrate or the relief structure of a casting tool. In an embodiment, one or more curable materials are applied to the relief structure of the casting tool to substantially completely fill the recesses of the relief structure defined in the surface of the casting tool, and a layer of one or more curable materials is formed on the elevations of the relief structure. Essentially the entire bulk of the curable material (including the portion within the recesses and the layer above the elevations) is cured and transferred to the substrate. In other words, one or more curable materials are not removed (“scrapered”) from the surface of the casting tool, or would otherwise be removed from the elevations, such that the surface relief structure remains on the substrate, which includes an integral base layer of one or more curable materials between the protrusions, as described above.

[0074] However, in alternative examples, the curable material is applied only to the recesses of the relief structure of the casting tool, preferably using a removal device such as a doctor blade, and the method further includes subsequently applying one or more curable materials to the relief structure, and applying an additional layer of said one or more curable materials, or another one or more curable materials, to substantially the entire surface of the casting tool before bringing the substrate and the casting tool together, to improve the retention of the one or more curable materials on the substrate. In such examples, the additional layer is used to improve the adhesion of the one or more curable materials—which are only located within the recesses of the relief structure of the casting tool—to the substrate. When the additional layer is applied substantially to the entire surface of the casting tool (i.e., on the surface of the tool surface where the relief structure fills the recesses and between these recesses), the resulting surface relief structure comprises an integral base layer as described. The curable material of the additional layer may be the same one or more curable materials as the curable materials used to form the elements of the surface relief structure, or it may be a different curable material.

[0075] According to another aspect of the present invention, a method for manufacturing a security document is provided, the method comprising: providing a document substrate; forming a security device on the document substrate or on a security device substrate fixed to or integrated into the document substrate, or forming a security device substrate; and then applying the security device substrate to the document substrate or bonding the security device substrate to the document substrate, wherein in each case one or more of the above methods are used to manufacture the security device. The method can be configured to provide a security document having any of the above-described preferred features.

[0076] During the manufacture of the safety device or safety document according to the present invention, the substrate may be processed in the form of a mesh or multiple sheets.

[0077] This document also discloses a safety article comprising a safety device according to any of the examples described above, preferably wherein the safety article is a safety wire, strip, insert, foil, or patch. The invention also provides a safety document including such a safety article.

[0078] A casting tool is also disclosed for forming a surface relief structure formed from one or more curing materials. The casting tool has a relief structure comprising a plurality of grooves having a first dimension, these grooves being spaced apart by raised regions, and wherein at least one (preferably at least some, more preferably each) of these grooves has a substructure having a second dimension smaller than the first dimension at its base and / or at least one (preferably at least some, more preferably each) of the raised regions between these grooves. Such a casting tool can be used to manufacture the device according to the invention as described above, preferably by a casting curing process. The substructure typically comprises a plurality of substructure elements. Attached Figure Description

[0079] Examples of safety devices and safety documents according to the invention, as well as methods of manufacturing them, will now be described with reference to the accompanying drawings, in which:

[0080] Figure 1 An example of a conventional security device is shown in the form of an intaglio print on a security document;

[0081] Figures 2(a) and 2(b) show Figure 1 A cross-sectional schematic diagram of the safety device;

[0082] Figures 3(a) to 3(d) The illustration schematically depicts the traditional gravure printing process;

[0083] Figure 4 The illustration shows another example of a printing feature that can typically be formed using gravure printing;

[0084] Figures 5(a) to 5(c) A cross-section of a portion of an example safety device is shown;

[0085] Figure 6 A cross-section of a portion of a safety device according to an embodiment of the present invention is shown;

[0086] Figure 7 The illustration shows a cross-section of a portion of a safety device according to another embodiment of the present invention;

[0087] Figure 8(a) shows an exemplary embodiment of a security document having the security device 10 according to the present invention in a plan view;

[0088] Figure 8(b) is a cross-sectional view of a portion of the safety device;

[0089] Figure 9 This is a perspective view of a part of a safety device according to an embodiment of the present invention;

[0090] Figures 10(a) to 17(b) The illustration shows a perspective view of a portion of a safety device according to various embodiments of the present invention;

[0091] Figure 18 This is a cross-sectional view of a portion of the safety device according to the present invention;

[0092] Figure 19 and Figure 20 The illustration shows a perspective view of a portion of a safety device according to another embodiment of the present invention;

[0093] Figure 21 This is a cross-sectional view of a portion of the safety device according to the present invention;

[0094] Figures 22(a) to 22(c) The illustration shows a perspective view of a portion of another safety device according to the present invention;

[0095] Figures 23 to 24(b) A cross-sectional view of a portion of the safety device according to the present invention is shown;

[0096] Figure 25 The illustration shows how the tactile sensation of different parts of an image can change depending on the image.

[0097] Figures 26(a) and 26(b) illustrate portions of the safety device according to the present invention;

[0098] Figure 27 A portion of a safety device according to another embodiment of the present invention is illustrated in perspective.

[0099] Figures 28(a) and 28(b) are cross-sectional views showing portions of the safety devices at different base layer heights;

[0100] Figure 29 This is a cross-sectional view of a portion of the safety device according to the present invention;

[0101] Figures 30(a) to 30(c) The illustration depicts a security document with a security device according to the present invention;

[0102] Figures 31(a) to 31(c) A cross-section of an example safety device including a decorative layer is shown;

[0103] Figure 32 A cross-section of another device according to the invention is shown, the device including a decorative layer;

[0104] Figure 33 It is a cross-sectional view of a device in which the substrate includes an integral decorative mark;

[0105] Figure 34 The illustration shows a cross-sectional view of a portion of a safety device according to another embodiment of the present invention;

[0106] Figures 35(a) to 35(c) The figure shows a cross-sectional view of a safety device including an embossed structure according to the present invention;

[0107] Figures 36 to 42 A further cross-section of the device including the embossing structure according to the present invention is shown;

[0108] Figure 43 An apparatus according to another aspect of the invention is shown;

[0109] Figures 44(a) to 44(e) A cross-section illustrates another embodiment of the safety device according to the present invention;

[0110] Figure 45 A further embodiment of the safety device according to the invention is shown in cross-section;

[0111] Figures 46(a) and 46(b) show in cross-section another embodiment of the safety device according to the invention;

[0112] Figures 47(a) and 47(b) illustrate a possible method for forming a surface relief structure according to the present invention using a casting and curing process; and

[0113] Figure 48 This is a schematic enlarged view of a portion of an example casting tool that can be used to form a surface relief structure according to the present invention. Detailed Implementation

[0114] The following description will focus on security devices formed directly on document substrates that ultimately serve as the basis for security documents such as banknotes, passports, certificates, licenses, and identity cards. However, as will be explained with reference to Figure 46(b), all embodiments of the security device can alternatively be formed on separate substrates for later application to (or incorporation into) security documents.

[0115] For comparison, Figure 1 An example of a conventional security device is shown in the form of an intaglio print 110 on a security document 100. Figure 1The security document 100, along with the enlarged portion of the intaglio printing, is shown in plan view, and Figure 2(a) shows a schematic cross-section along line Q-Q'. It should be noted that, for simplicity, Figure 2(a) does not show the imprinting properties of the substrate, which are caused by the intaglio printing and exist in practice. This is shown in enlarged detail in Figure 2(b). In this example, the intaglio printing is shown as being formed on a document substrate 2, which consists of an inner core substrate 2a and an outer opaque layer 2b (e.g., white ink), the inner core substrate 2a being a polymer material such as BOPP. This is a typical construction of polymer banknote substrates. However, the intaglio print 110 can be formed on any document substrate, including paper substrates.

[0116] like Figure 1 As shown, in this example, the gravure print 110 includes a line image of a kingfisher. The kingfisher image is multi-colored and consists of an array of image elements 112 in the form of spaced ink lines of varying sizes and spacing, configured as needed to express the characteristics of the image. (Reference) Figures 3(a) to 3(d) The gravure process involves providing a printing plate 500 in which all lines 510 of the desired image element 112 are etched (shown in FIG. 3(a)). Ink 114 is applied to the corresponding area of ​​the printing plate corresponding to the desired image element 112 (FIG. 3(b)). The ink is pressed into the etched lines 510 and the middle surface of the plate is cleaned using a wiping blade or the like. The printing plate 500 is then pressed against a pressure roller (not shown) onto a substrate 2 under high pressure, pressing the substrate 2 into the etched lines (FIG. 3(c)), thereby causing the substrate 2 to be imprinted. After separation, the ink 114 is transferred from the printing plate to the top of the raised elements of the now imprinted substrate 2 (FIG. 3(d)). The raised elements and the ink carried thereon form the image element 112 of the gravure print 110. For completeness, Figures 3(a) to 3(d) The process of “blind printing” is also schematically illustrated, in which no ink is applied to the printing plate 500, but the substrate is printed as shown in image element 112 in region B of the substrate in Figure 3(d).

[0117] The embossing properties of printed matter 110 provide tactile quality. However, the tactile quality provided by gravure printing is limited by the amount of ink that can be transferred onto the substrate 2 and the amount of thermal / pressure deformation that the substrate can withstand / retain. Specifically, polymer-based substrates (as commonly found on banknotes) have lower thermal stability and cannot be embossed like paper, resulting in a lower gravure profile. Furthermore, conventional gravure processes lead to numerous problems, such as difficulty in controlling subsequent printing processes (“flowering”), smudging, and potential damage to vulnerable components, such as optically variable inks and foils, as described above.

[0118] Figure 4Another example of a typical printing feature is shown in a plan view, which is typically formed using gravure printing. In embodiments of the invention, such as... Figure 1 and Figure 4 The features shown can be formed by casting-curing surface relief structures rather than (and) gravure printing. Figure 1 and Figure 4 The example shown is a multi-tone image composed of a series of halftone elements—in this case, line elements—with varying thicknesses and / or spacing across the device to give the appearance of different tones. However, any image presented by this device does not need to be multi-tone.

[0119] Figure 5(a) shows a schematic cross-section of a portion of any of the devices, from which it can be seen that the individual elements 21 are formed as raised elements in a surface relief structure 20 by a casting-curing process, the surface relief structure 20 being formed of a cured material 20a. Preferably, this material is translucent and contains a visible colorant to create a contrast with the underlying substrate. The base layer 29 of the material extending between the raised elements 21 is preferably thin enough to have a much lower optical density than the raised elements, such that the contrast between them is visible.

[0120] The size, spacing, and / or height of the protruding elements 21 can be varied throughout the device by appropriate design of the casting mold in order to express the desired screen image or other features.

[0121] Typical parameters for forming conventional gravure grooves for known printed elements are given below. If desired, the relief on the casting tool used to form the cast-cured raised element according to an embodiment of the invention can be configured to have the same or similar parameters:

[0122] For paper-based substrates:

[0123] The linewidth of the grooves containing ink / printed material typically ranges from 50 μm to 8 mm, more preferably from 50 μm to 3 mm, and even more preferably from 50 μm to 1 mm.

[0124] The linewidth of the grooves containing only the embossed portion (without ink) typically ranges from 30 μm to 8 mm, more preferably from 30 μm to 3 mm, and even more preferably from 30 μm to 1 mm.

[0125] The minimum gap between grooves is typically 30 μm.

[0126] The depth of the trench typically ranges from 20 μm to 150 μm, more preferably from 25 μm to 125 μm, and even more preferably from 35 μm to 90 μm.

[0127] For polymer substrates:

[0128] The linewidth of the grooves containing ink / printed material typically ranges from 50 μm to 8 mm, more preferably from 50 μm to 3 mm, and even more preferably from 50 μm to 1 mm.

[0129] The linewidth of the grooves containing only the embossed portion (without ink) typically ranges from 30 μm to 8 mm, more preferably from 30 μm to 3 mm, and even more preferably from 30 μm to 1 mm.

[0130] The minimum gap between grooves is typically 30 μm.

[0131] The depth of the trench typically ranges from 10 μm to 100 μm, more preferably from 15 μm to 85 μm.

[0132] Even more preferably, it is 20μm to 55μm.

[0133] Cast-curing can theoretically match these parameters (and is advantageously substrate-independent, as discussed above), with the only limitation being the thickness of the UV resin that can be effectively cured. Cast-curing has no depth limitations on polymer substrates, while gravure does. Specifically, cast-curing techniques can produce larger, smaller, and / or more complex structures than gravure (provided the curable material can be cured) because these processes are not constrained by the inks, prints, or imprints of conventional gravure.

[0134] In all embodiments, it will be understood that the size (e.g., height, width), shape, orientation, and / or spacing between the cast protruding elements may vary.

[0135] Figures 5(b) and 5(c) are perspective views of portions of the corresponding devices, illustrating a plurality of raised protrusions 21 connected by a base layer 29. The raised protrusions 21 are in the form of elongated linear elements and can define, for example, image elements of a halftone image. Therefore, the raised protrusions can be considered as raised elements. In both cases, when a user moves their finger along the length of the raised element in the x-axis direction, the surface relief structure 20 will have a relatively smooth tactile feel. However, when the user moves their finger along the y-axis perpendicular to the length of the element, the surface relief structures of Figures 5(b) and 5(c) will exhibit different levels of tactile feel due to the difference in the spacing between the elements, where the spacing in Figure 5(c) is smaller than that in Figure 5(b) (and therefore has a smoother tactile feel).

[0136] The security level of a device can be improved by adding various features. Control over the tactile sensation exhibited by the surface relief structure can be increased by adding substructures, which will now be described. This additional control over the tactile sensation advantageously enhances the security level of the device.

[0137] exist Figure 6 and Figure 7 In this design, substructures (generally shown as 30) are provided on the top of the raised elements 21 and / or on the base layer 29 in the recesses 23 between the raised elements 21. The substructure 30 is smaller than the scale of the relief elements 21 themselves, for example defining multiple peaks and depressions on the top of a single raised element. This can be achieved by providing a suitable substructure relief within a groove for casting molds from which the raised elements are cast. Due to the nature of the casting-curing process, these will be faithfully replicated in the finished product.

[0138] It will be understood that, within the same device, the first-level structures 21 (protruding elements) can differ from each other—for example, having different heights and widths and / or shapes. Similarly, the second-level structures 30 (substructures) within the same device can also differ from each other—for example, having a coarser / finer structure / feel. All combinations of the two are also envisioned.

[0139] exist Figure 6 and Figure 7 In the example shown, substructure 30 is a tactile structure, allowing control over the degree of tactile sensation throughout the safety device, and enabling variation across the entire safety device if needed. For example, Figure 6 An example is shown below: in one region, the protruding element 21 has a substructure on its top that feels relatively rough to the touch, while in another region, the protruding element 21 has a relatively smooth substructure on its top. Figure 7 In the example, the tops of the protruding elements are made relatively rough, while the recesses 23 between them are provided with a tactile structure that feels relatively smooth. In a preferred embodiment, this is an asymmetrical structure, feeling smoother in one direction than in the opposite direction. This asymmetry will be discussed in further detail herein.

[0140] Figures 8(a) and 8(b) illustrate exemplary embodiments of a secure document 100 having a security device 10 according to the invention. Figure 8(a) shows the document 100 and device 10 in a plan view including the enlarged portion, and Figure 8(b) shows a schematic cross-section of the device 100 taken along line XX′. Again, in this example, the document substrate 2 is shown as a multilayer substrate having a transparent polymer core substrate 2a (e.g., BOPP) and an opaque layer 2b on either side. In practice, multiple opaque layers will be used to achieve the desired opacity. In this example, the security device 10 is positioned in a non-window area (i.e., with opaque layers on both sides of the polymer core substrate in this area of ​​the device 10) and is intended to be observed in reflection, but other arrangements of the device in window and half-window areas are contemplated, as will be outlined in more detail herein. The substrate does not show localized raised areas and recesses caused by embossing (as shown in Figure 2(b)) and is therefore referred to as “flat”.

[0141] Device 10 presents with Figure 1 A line image of the same kingfisher (e.g., a macroscopic image) consists of an array of spaced image elements 11, which vary in size, shape, and / or spacing, for example, throughout the image, to express the characteristics of a multi-tone halftone image (e.g., the kingfisher's head, eyes, beak, etc., appear in different hues), as shown more clearly in the magnified portion of Figure 8(a). The image elements are preferably sized such that they can be individually distinguished under close examination or at low magnification.

[0142] As schematically illustrated in Figure 8(b), the safety device 10 includes a surface relief structure 20 disposed on a first surface 3a of a substrate 2, wherein in this example, the first surface 3a of the multilayer substrate 2 is the first surface of an opaque layer 2b. The surface relief structure 20 is formed of a continuum of cured material 20a having a profile with varying height (parallel to the y-axis). The surface relief structure 20 includes a first-level set of relief elements in the form of raised protrusions 21. The raised protrusions correspond to image elements 11 presented by the device and can therefore be referred to as raised elements. Here, the size and spacing of the raised elements vary throughout the surface relief structure 20 to express a multi-toned image of a kingfisher. For example, raised elements 21a and 21b have different sizes (e.g., widths parallel to the x-axis), and the spacing between raised elements 21a and 21b is greater than the spacing between raised elements 21b and 21c. Due to the variation in the size and spacing of the raised elements 21, an observer of the device will perceive corresponding areas of the image as exhibiting different hues, thus presenting the multi-toned image of the kingfisher shown in Figure 8(a).

[0143] As can be seen in Figure 8(b), the raised elements 21 of the surface relief structure 20 are connected to each other by a base layer 29 of the same cured material 20a, which extends between each raised element. The base layer 29 is the product of the casting-curing process used to form the surface relief structure 20. The base layer is preferably thin enough (in the direction parallel to the y-axis) to have a much lower optical density than the raised elements 21, so that the contrast between them is visible. If desired, the height (e.g., “thickness”) of the base layer 29 can be varied throughout the surface relief structure to provide further optical effects due to the variation in optical density in regions of different base layer heights.

[0144] The surface relief structure 20 also includes a second-level relief element set 31 defining the tactile structure 30. In the region X-X' of the device illustrated in FIG8(b), the tactile structure 30 is only disposed on top of the raised element 21, and the second-level relief element set (referred to herein as the "tactile protrusion") 31 takes the form of an elongated symmetrical linear microprism extending into the plane of the page, such as... Figure 9 This is illustrated more clearly in Figure 8. While the surface relief structure 20 will exhibit an inherent tactile feel due to the raised elements 21 (i.e., the first-level relief structure), the tactile structure 30 provides additional control over the tactile feel experienced by the user. The tactile feel of the tactile structures 30 (e.g., the degree to which they are perceived as rough or smooth) is defined at least in part by the height, spacing (pitch), shape, and / or orientation of the tactile protrusions 31. The height d of each tactile protrusion 31 (e.g., the distance between the tops of the raised protrusions and the tops of the tactile protrusions here, “protrusion height”) corresponds to the depth of the corresponding recess in the tool that forms it. Generally, an increased height of the tactile protrusions 31 results in an increased roughness of the corresponding tactile structure 30. An increased pitch of the tactile protrusions 31 generally results in an increased roughness of the corresponding tactile structure 30. The shape of the tactile protrusions also generally contributes to the tactile level of the tactile structure. In the examples shown in Figures 8(a) and 8(b), the tactile structure 30 exhibits a relatively high level of tactile feel (roughness). The orientation of tactile protrusions can also be used to control the tactile sensation of the sensing device, and particularly advantageously allows for directional control of the sensed tactile sensation.

[0145] When the tactile protrusion 31 is in the form of an elongated linear microprism, the resulting tactile structure 30 has an asymmetrical arrangement because the perceivable will perceive differences in tactile level when the perceivable moves their fingers along the surface relief structure in different directions. Refer to Figures 8(a), 8(b), and... Figure 9When an observer moves their finger along the entire surface relief structure 20 in the x-direction, they will experience a relatively rough texture due to the multiple peaks and depressions defined by the microprisms. When they move their finger along the z-direction (i.e., along the length of the extended microprisms), the tactile structure will exhibit a smoother texture because the peaks and depressions defined by the microprisms will be less perceptible.

[0146] Figures 10(a) to 20 A further example is illustrated where a substructure 30 is disposed on top of a protruding element 21. Figure 10(a) illustrates a surface relief structure 20 with multiple protruding elements 21 (as shown in Figure 5(b)), wherein each protruding element has a substructure 30 on top in the form of a tactile structure. Each tactile structure 30 includes multiple tactile protrusions 31 oriented in the form of symmetrical linear microprisms oriented in a cross direction relative to the elongation direction of the linear protruding element 21. Therefore, in contrast to the relief structure of Figure 5(a), the tactile structure 30 produces a coarser tactile sensation when the user moves their finger along the x-axis. Different levels of tactile sensation are also perceived along the y-axis.

[0147] In Figure 10(b), the tactile structure 30 disposed on top of the protruding element 21 also includes an array of linear microprisms 31, but has a smaller pitch (increased periodicity) compared to the tactile structure 30 in Figure 10(a). Therefore, the surface relief structure 20 in Figure 10(b) will have a lower tactile level along the x-axis compared to the structure in Figure 10(a). The tactile structure 30 may cover only a portion of the corresponding protruding element, as shown in Figure 10(c).

[0148] Figures 11(a) to 11(c) Further examples of tactile structures 30 that can be used to control the tactile level of a surface relief structure are illustrated. In these examples, the tactile structure 30 presents gaps between various tactile protrusions 31. In Figure 11(a), the tactile structure 30 presents periodic gaps between the various tactile protrusions 31, wherein the tactile protrusions 31 are positioned in the same relative positions on the respective protrusion elements 21. In Figure 11(b), the gaps between the various tactile protrusions 31 are periodic within each tactile structure 30, but the relative positioning of the tactile protrusions on different protrusion elements varies. In Figure 11(b), the arrangement of the tactile structures 30 is reversed. In Figure 11(c), the arrangement of the gaps between the various tactile protrusions 31 is non-periodic (e.g., random).

[0149] Figure 12An exemplary surface relief structure 20 is illustrated, in which the tactile protrusion 31 is in the form of an asymmetrical prism structure. Here, facet 31a defines a sharper angle with the top of the protrusion element 21 compared to facet 31b. Therefore, when a user moves their finger along the x-axis in different directions, they will experience different levels of tactile sensation. When moving along the x-axis from right to left, the surface relief structure will present a coarser level of tactile sensation than when moving from left to right.

[0150] exist Figure 13 In this example, the tactile structure 30 includes an array of two tactile protrusions 31. The arrays are substantially identical (an array of symmetrical linear microprisms), but arranged in reverse phase. In other examples, the arrays may define different structures and / or be arranged with any degree of phase relationship.

[0151] Figure 14 Another example of a surface relief structure is illustrated, demonstrating how the orientation of the tactile protrusions 31 can be used to control the perceived tactile sensation presented by the device. Here, the tactile protrusions 31 are in the form of linear microprisms, but instead of their long axes, they are aligned in a direction intersecting the long axis of the first-level relief element 21, which is parallel to the elongation direction of the first-level protrusion element 21. Therefore, when a user moves their finger along the length direction of the protrusion element 21 (along the x-axis), the user perceives a relatively smooth tactile level, while in the intersecting direction (along the y-axis), a relatively rough tactile level is perceived. Furthermore, Figure 14 The microprism 31 in the middle has an asymmetrical cross section, which produces a difference in tactile level depending on the direction of the user's finger along the y-axis.

[0152] exist Figures 8(a) to 14 In the example shown, the tactile structure is in the form of an array of microprisms 31. These provide directional tactile levels; in other words, the tactile level depends on the direction in which the user's finger travels along the surface relief structure. Figure 15 The illustration depicts a surface relief structure 20 comprising multiple raised linear elements 21 as described above, each raised linear element 21 having a tactile structure 30 formed by multiple tactile protrusions 31 in the form of a square-based pyramidal structure. The linear microprism presents the primary tactile component in one direction (perpendicular to the elongation direction), while... Figure 15 The pyramid structure presents the primary tactile components in two directions (here along the x-axis and y-axis).

[0153] Tactile protrusions with more than two primary tactile components are also envisioned, such as hexagonal pyramidal structures, hemispheres (see Figure 16(a)), cones (Figure 16(b)) or cylinders (“rods”).

[0154] In Figures 16(a) and 16(b), the raised elements 21 formed on each tactile structure are in the form of a continuous "woodcut print," defining a portion of the image presented by the device 10. For example, the woodcut print can be used in combination with multiple halftone image elements to present a complete image.

[0155] The tactile structure may include different tactile protrusions, as schematically illustrated in Figures 17(a) and 17(b). In Figure 17(a), the surface relief structure 20 includes tactile protrusions 31-1 in the form of symmetrical linear microprisms and tactile protrusions 31-2 in the form of a pyramid structure. In Figure 17(a), the individual tactile protrusions within a particular tactile structure are identical, but in alternative embodiments, the tactile protrusions may vary within a single tactile structure 30, as shown in Figure 17(b). It is also noted from Figures 17(a) and 17(b) that the height of the individual tactile protrusions (and therefore the tactile structures) may vary across the entire surface relief structure to further control the presented level of tactile sensation.

[0156] In the examples to date, the tactile protrusion 31 typically includes angled facets formed by vertices or edges. Figure 18 This is a schematic cross-sectional view of a safety device according to another embodiment of the invention, wherein the tactile protrusion 31 is in the form of a cylindrical element (or "rod") extending from the top of the protruding element 21 and having a square wave profile in the cross-section. Figure 19 The illustration shows another exemplary embodiment in which the tactile protrusion 31 has a curved surface. This tactile protrusion can take the form of a regular curved element (as shown) or an irregular element. In some examples, the tactile structure may include a continuous element having features at a smaller scale than the first-level relief element 21.

[0157] Figure 20 An example is illustrated in which the tactile protrusion 31 includes an additional substructure, which is shown here as an elongated strip 31a disposed on the curved surface of the tactile protrusion 31.

[0158] exist Figures 8(a) to 20 For simplicity, the tactile structure 30 is shown as being located only on top of the first-level relief element (raised element) 21. Figure 21 A schematic cross-sectional view of the safety device is shown, in which the tactile structure 30 is disposed only in the recess 23 between the protruding elements 21. Figure 21 In the example, tactile protrusions 31 are formed on a base layer 29 that extends between protruding elements 21.

[0159] Figures 22(a) to 22(c)Another example of a surface relief structure 20 is shown in a perspective view, which includes a tactile structure 30 disposed only in the recesses between the protruding elements 21. In FIG. 22(a), the tactile protrusion 31 is in the form of a pyramid based on a square; in FIG. 22(b), the tactile protrusion 31 is in the form of a curved structure; and in FIG. 22(c), the tactile protrusion 31 is in the form of a curved structure having additional substructures 31a in its surface.

[0160] Typically, tactile structures can be located on top of protrusions, in recesses, or a combination of both. Figure 23 The figure shows a cross-sectional view of the safety device, wherein the tactile structure 30 is disposed on the top of the protruding element 21 and in the recess between the protruding elements 21.

[0161] Combinations of different tactile structures exhibiting varying levels of roughness / smoothness can be used within the same surface relief structure to provide further control and complexity to the overall tactile effect presented by the device, thereby enhancing the level of safety. Such an implementation is schematically illustrated in Figures 24(a) and 24(b), where the surface relief structure 20 includes tactile structures 30 exhibiting different levels of tactile sensation. In Figure 24(a), the tactile structure 30 is only disposed on the top of the protruding element 21, and not in the recess. In region A of the surface relief structure 20, the tactile protrusion is in the form of an elongated linear microprism, thereby giving the tactile structure 30-1 a relatively rough feel, and in region B of the surface relief structure, the tactile protrusion 31 is in the form of a rod structure, causing the tactile structure 30-2 to exhibit a relatively smooth feel.

[0162] In Figure 24(b), tactile structures 30 are present on the top of the raised elements 21 and in the recesses 23 between the raised elements 21. In this example, the tactile structure 30-1 on the top of the raised elements 21 (regions A1 and A2 of the surface relief structure 20) provides a relatively rough tactile feel, while the tactile structure 30-2 on the base layer 29 in the recesses 23 (region B) provides a smooth feel when the user moves their fingers across the device.

[0163] The tactile sensation can be varied based on the image presented by the surface relief structure in order to provide a particularly secure device. For example, referring back to the image of the kingfisher in Figure 8(a), the level of tactile sensation of the tactile structure 30 may vary throughout the device, such as... Figure 25 The illustration is schematic. Figure 25 Four distinct regions of the surface relief structure 20 are illustrated by way of example. The surface relief structure 20 has a tactile structure 30 that varies according to the corresponding parts of the image. Figure 25The illustration shows a portion of a surface relief structure 20 corresponding to the beak of a kingfisher: that is, the raised elements 21 in this region of the surface relief structure 20 correspond to the line image elements defining the beak. A tactile structure 30, including an asymmetrical prism structure, is disposed on top of the raised elements 21 to provide an asymmetrical, high tactile feel along the x-axis (along the direction of the beak). Figure 25 In the area of ​​the surface relief structure 20 shown in (b), the tactile protrusion 31 is in the form of a curved structure, giving a smooth tactile feel consistent with the chest of a kingfisher. Figure 25 (c) shows the area of ​​the surface relief structure corresponding to the wings, and this tactile structure includes a non-periodic spaced prism structure. Figure 25 In (d), the raised element 21 is in the form of a continuous print defining a fern leaf, wherein the tactile structure 30 includes a plurality of straight cones disposed on the top of the raised element, providing a substantially symmetrical tactile effect.

[0164] In the examples discussed so far, the first-level relief element set 21 of the surface relief structure 20 all have the same height. Figure 26(a) illustrates a cross-sectional view of the safety device according to an embodiment of the invention, wherein the first-level relief element set 21 (again, in the form of raised elements corresponding to the corresponding image elements of the image presented by the device) have different heights throughout the surface relief structure. For example, each raised element 21-1 has the same height h1 above the base layer, which is lower than the height h2 of the raised element 21-2 above the base layer. The surface relief structure 20 includes a tactile structure 30 disposed on top of each raised element 21. In this example, the tactile structure 30 on top of the raised element 21-1 has a relatively rough tactile level. The tactile structures 30 on top of the raised elements 21 have different tactile levels, wherein the tactile structure in region A provides a relatively rough feel, while the tactile structure in region B forms a smooth structure. Variations in the height of the raised elements in the first-level relief structure can provide perceptible tonal differences in the presented image (e.g., differences in light density due to variations in the thickness of the cured material through which light needs to pass), as well as introduce additional tactile effects throughout the surface relief structure.

[0165] Figure 26(b) shows a perspective view of another example of a surface relief structure in which the heights of the first-level relief element set 21 are different. In Figure 26(a), the individual relief elements 21 have different heights, while Figure 26(b) shows an example in which the individual relief elements 21-1 have different heights within their domains.

[0166] Figure 27An exemplary surface relief structure is illustrated, wherein the height of the raised element 21 varies continuously over its domain. In this example, the raised element takes the form of a prism structure with an asymmetrical cross-section, thereby providing directional tactile feedback in directions intersecting its elongation direction. Tactile protrusions 31 forming tactile structures 30 on the top of the raised element further contribute to the overall tactile effect.

[0167] As discussed, the raised elements 21 of the surface relief structure 20 formed during the casting and curing process are connected together by a base layer 29 of the same cured material. As schematically shown in Figures 28(a) and 28(b), the height of the base layer 29 can vary throughout the surface relief structure to provide further tactile or optical effects. In the surface relief structures of Figures 28(a) and 28(b), the base layer 29 includes a region 29-1 with a relatively increased height (thickness). In Figure 28(a), each raised element 21 has the same individual height (indicated by h) above the base layer, which corresponds to the depth in the groove of the casting tool, and therefore the top of the raised element 21 located in the raised region 29-1 of the base layer has a greater height above the substrate compared to the top of the raised element located on the lower part of the base layer. Therefore, the height of the tactile structure 30 above the substrate 2 varies throughout the surface relief structure, further increasing the complexity of the tactile effects.

[0168] In Figure 28(b), the heights (h1) of the protruding elements 21 on the raised area 29-1 of the base layer are smaller than the heights (h2) of the protruding elements disposed on the lower part of the base layer, such that the top of the protruding elements 21 (and thus the tactile structure) has the same height above the substrate on the entire surface relief structure.

[0169] Figure 29A schematic cross-section of a portion of another device is shown, in which the heights of the tactile protrusions 31 of the tactile structure 30 vary to compensate for the height difference between the entire first-level embossed element set 21 and the base layer. Thus, the tops of the tactile protrusions 31 have a substantially uniform height (or thickness of the curable material) H over the entire surface embossed structure above the substrate. For example, the individual tactile protrusions 31 on the top of the raised protrusions 21 in region A have a smaller protrusion height compared to the tactile protrusions 31 within the recesses in region B of the device. In this way, the tops of each tactile protrusion of the surface embossed structure have substantially the same height above the surface 3a of the substrate 2, but due to the differences in the protrusion heights of the individual tactile protrusions 31, the surface embossed structure still exhibits perceptible tactile variations over its domain. Such an implementation is particularly advantageous when it is desired that the security document on which the device is located or integrated is of substantially uniform thickness to improve the shape of the paper stack and document handling, because the surface embossed structure can be used to compensate for local variations in document thickness, such as in window areas defined by local absences of opaque layers. In another example, the surface relief structure 20 can be configured to have a total height that is substantially the same as that of individual features on the document.

[0170] Figures 30(a) to 30(c) The illustration shows another embodiment of the invention in which directional tactile sensation provided by a tactile structure is used to provide a security device. Figure 30(a) illustrates a security document 100, in this case a banknote. The banknote includes a device having two surface embossed structures 20a, 20b. Each surface embossed structure includes a plurality of raised elements 21 in the form of image elements defining a “£” symbol. A plurality of tactile protrusions 31 in the form of an asymmetrical prism structure are disposed on top of each raised element 21. The arrangement of the tactile protrusions 31 of structure 20a is substantially opposite to that of structure 20b, such that although the two surface embossed structures 20a, 20b present the same image, they provide different directional sensations along the x-axis. More specifically, the image presented by the first structure 20a feels relatively rough when the user moves their finger along the x-axis from right to left, and relatively smooth when moving from left to right. Conversely, structure 20b feels relatively rough when moving from left to right, and relatively smooth when moving from right to left. This difference in directional tactile feedback, associated with the same features as other aspects, provides a particularly secure document.

[0171] Figure 30(b) illustrates a similar example. Here, although the orientation of the images is reversed as defined by the raised elements, the tactile structures have the same arrangement on both structures 20a, 20b. Although Figures 30(a) and 30(b) illustrate individual surface relief structures 20a, 20b, in alternative embodiments, a single surface relief structure (i.e., a single continuous block of cured material) may include different regions formed in the manner described above.

[0172] Figure 30(c) illustrates a security document 100 similar to that illustrated in Figure 30(a), wherein a surface embossed structure is provided on the opposite side of the document substrate.

[0173] In an improvement to the invention, the surface relief structure 20 can be combined with a decorative layer to provide a further sophisticated effect that increases the security level of the device, as will now be referred to. Figures 31(a) to 32 As described.

[0174] Figure 31(a) illustrates a cross-sectional view of a safety device comprising a decorative layer 35 in the form of a printed layer applied to the surface 3a of a substrate 2. In this example, the substrate 2 is a paper substrate and the printed layer 35 is formed by offset printing; however, it should be understood that the printed layer can be formed by other printing processes such as gravure printing, offset printing, flexographic printing, inkjet printing, or any other convenient method. Here, the cured material of the surface embossed structure 20 is substantially transparent and colorless, wherein the first-level embossed element set is in the form of raised elements 21 corresponding to the image elements of a multi-tone image. The printed layer can be used to provide color for the multi-tone image presented by the surface embossed structure 20, wherein the printed layer is visible through the transparent cured material of the surface embossed structure.

[0175] Therefore, the printed layer can take the form of an area of ​​the same color as the surface embossed structure 20, making the multi-tone image presented by the surface embossed structure 20 appear colored. In other examples, the printed layer 35 can define image elements that are substantially the same as the raised elements 21 of the surface embossed structure, wherein the image elements of the printed layer and the raised elements of the surface embossed structure are set in a registration (i.e., overlay alignment, or "overlay"). As shown in FIG31(a), the printed layer 35 can be in the form of substantially covering the entire substrate 2 or at least most of it, such as 50% or more of the printed matter. This is especially true when the security document is a banknote, where a decorative printed layer in the form of lithographic printing can be applied to the surface of the substrate before casting the surface embossed structure 20 in a conventional banknote production workflow. In other examples, the printed layer 30 can cover an area smaller than the surface embossed structure 20. For example, the printed layer can be laterally entirely within the lateral boundaries of the surface embossed structure.

[0176] In Figure 31(b), the decorative layer 35 is in the form of an optically variable layer, particularly a color shift layer, which is a liquid crystal film disposed on the paper substrate 2. Similar to the example of the printed layer described above, the color shift layer can be configured (e.g., printed) to define image elements substantially the same as the raised elements of the surface relief structure 20, or it can be configured to have a different form from the surface relief structure. In Figure 31(c), the decorative layer 35 is in the form of a holographic foil, and the substrate 2 is also a paper substrate. It should be noted that the arrangement of the surface relief structure on fragile decorative layers (such as liquid crystal films and holographic layers) seen in Figures 31(b) and 31(c) would be very difficult or impossible to achieve using conventional gravure printing, because the high temperature and pressure involved in the gravure process, together with the imprinting on the substrate, would usually damage such features. Therefore, the combination of the surface relief structure and the decorative layer in these embodiments provides a device that is particularly difficult to counterfeit.

[0177] exist Figures 31(a) to 31(c) In the example, both the decorative layer 35 and the surface embossing structure 20 are disposed on the same surface 3a of the paper substrate. However, in alternative embodiments, it is contemplated that the decorative layer 35 and the surface embossing structure 20 may be disposed on opposite surfaces of transparent or translucent areas of the substrate 2 (such as window or half-window areas of polymer-based substrates). In such an embodiment, the surface embossing structure and the decorative layer are arranged to at least partially overlap, such that their combined effect can be observed at least from one viewing angle.

[0178] Figure 32 Another embodiment similar to that shown in FIG. 31(b) is illustrated. In this embodiment, the decorative layer 35 is in the form of a color-shifting film, and the surface embossing structure 20 is configured to encapsulate the color-shifting film, i.e., to completely cover the film and seal it from the atmosphere or any external environment. Here, the base layer 29 of the surface embossing structure 29 extends laterally around the periphery of the raised element 21 to encapsulate the decorative layer 35. In this way, the color-shifting film 35 can be protected from external influences, and the service life of the security device can be extended. Although this embodiment is described with reference to a decorative layer in the form of a color-shifting film, it should be understood that the surface embossing structure can be used to encapsulate and protect essentially any decorative layer. This type of embodiment is particularly advantageous when the decorative layer is in the form of a metallic layer, because metallic elements are generally susceptible to corrosion by alkaline components. Encapsulating the decorative layer with the surface embossing structure as a chemical barrier prevents alkaline or other corrosive materials from contacting the metal. In an extension of this aspect of the invention, the curing material of the surface embossing structure can be used as a protective outer layer of the security document 100, for example, in a manner similar to the outer paint layer of a banknote.

[0179] In a further development of the invention, increased complexity can be achieved by additionally providing an integral decorative mark 60 in the substrate 2, such as... Figure 33 As illustrated in the diagram. The decorative markings are formed during the manufacturing of the document substrate, not applied to the substrate during subsequent processing (as shown in the reference). Figures 31(a) to 32 (Description of the decorative layer). Typically, the decorative mark can be integrated into a multilayer polymer document substrate during the same process as applying the opaque layer 2b to the core substrate 2a, for example via gravure printing. Thus, the integrated decorative mark 60 will be precisely aligned with the opaque layers 2b, and especially with any window or half-window area defined by them. Such decorative marks can be incorporated into the security devices disclosed herein by arranging one or more surface embossed structures to partially or completely overlap with or otherwise interact with the decorative mark 60 (e.g., appearing adjacent to, surrounding, or interlocking with the decorative mark). Although integrated decorative marks typically take the form of printed matter as described above, they can include or take the form of other elements or components, such as optically variable parts (e.g., color-shifting layers or holographic foil), or reflective / metallic parts as described above with reference to embodiments including decorative layers.

[0180] In embodiments where the security device includes a decorative layer and / or decorative markings in the form of printed material, the markings can be applied using standard, one or more visible colored inks. To further enhance the security level, in other embodiments, the markings may include one or more substances that respond to one or more invisible wavelengths (preferably UV or IR), and the markings may optionally be invisible under white light. For example, the printed material may include pairs of inks that appear to match each other under one lighting condition (e.g., white light) and different from each other under another lighting condition (e.g., UV light). Examples of suitable materials from which a printed layer can be formed are disclosed in WO-A-2004 / 050376 and WO-A-2018 / 206936. In other examples, the printed material may include substances that emit red, green, and blue light when irradiated by corresponding excitation bands. Examples of suitable substances are disclosed in WO-A-2020 / 030893.

[0181] In the examples discussed above, the cured material for the surface relief structure is at least partially transparent and colorless. However, the cured material may contain visible colorants. As mentioned above, such visible colorants may be visible under white light or may respond to one or more invisible wavelengths (such as UV or IR).

[0182] In the examples described so far, we have discussed substructures that define the tactile structure, providing enhanced control over the tactile sensation of the surface relief structure. Alternatively or additionally, the substructure may define optical elements, such as prisms, mirrors, focusing elements, or caustic structures, to provide additional optical effects to the device. Figure 34 An example is illustrated in the diagram. Figure 34 This is a cross-sectional view of such a device. Here, the surface relief structure 20 includes a plurality of first-level relief structures 21 and a set of second-level relief structures in the form of cylindrical lenses 33, which are formed of a substantially transparent cured material (but other lens geometries such as spherical lenses may be used depending on the desired optical effect). The cylindrical lenses are positioned on top of raised protrusions in the form of raised platforms 21a. The raised protrusions 21-1, 21-2 of the first-level relief element set define elements of an image presented by the device (e.g., halftone). The surface relief structure 20 is formed on a paper substrate 2, and a decorative layer 35 has been applied to the first surface 3a of the paper substrate 2. In this example, the decorative layer is in the form of a printed layer presenting an array of micro-image elements. The array of cylindrical lenses 33 is applied to be superimposed and aligned with the printed layer, such that the lenses 33 and the micro-image elements of the printed layer cooperate to present optically variable effects, such as lenticular image switching effects or moiré magnification effects. The height of the raised platforms 21a is such that the decorative layer 35 is substantially within the focal plane of the cylindrical lenses.

[0183] Due to the presence of the protruding elements 21-1 and 21-2, and the optically variable effects generated by the cooperation of the cylindrical lens 33 and the decorative layer 35, such a device will present (e.g., a halftone) image. This produces a particularly secure device that is very difficult to forge.

[0184] In a variant of this embodiment, the decorative layer can be formed on opposite surfaces. In this case, the formation of the surface relief structure 20 and the formation (e.g., printing) of the decorative layer can be performed simultaneously, occurring at the same location along the machine direction. This achieves the highest level of registration between the two components of the safety device, as no slippage or deformation of the substrate occurs after one step and before the next (because there is no interval between the two steps). Suitable apparatus for simultaneously casting-curing and printing on opposite sides of a substrate is disclosed in WO-A-2018 / 153840 and WO-A-2017 / 009616. The level of registration that can be provided by simultaneous casting and printing using the apparatus disclosed therein cannot be achieved on a rotary printing press or in two separate processes.

[0185] So far, we have considered methods to improve the safety level of the device by adding substructures. Figure 35(a) shows an example where the safety device includes a casting-curing structure (typically indicated by 80) and an inked impression portion formed by gravure (typically indicated by 90). In Figure 35(a), gravure elements 91 are arranged on top of the casting-curing structure 80 in recesses 83 between protrusions 81, wherein the gravure elements are disposed on the base layer 89 of the casting-curing structure 80. The casting-curing structure 80 may be formed of an elastomeric curing material (examples can be found in WO2017 / 009620; e.g., page 34, lines 22 to 35, lines 11) to facilitate gravure printing processes after the casting-curing structure is laid, but this is not necessary. Figure 35(b) shows another example where the gravure elements 91 are disposed on the base layer of the casting-curing structure 80. In the example of Figure 35(b), the gravure element 91 is laterally spaced from the raised protrusion 81 of the casting structure 80, rather than being completely integrated with the casting structure as in Figure 35(a).

[0186] In other embodiments, the inked embossed portion 90 formed by the gravure can be provided adjacent to the casting-curing structure, as shown in FIG35(c), wherein the gravure element 91 is directly disposed on the substrate 2. In FIG35(c), the casting structure 80 and the inked embossed portion are laterally spaced apart, but in alternative embodiments they can be adjacent to each other.

[0187] In addition to the surface relief structure formed by casting-curing, the use of embossed structures advantageously provides further tactile and / or optical effects that can be perceived by an observer. Typically, the elements of the inked embossed portion define the elements of the image, such that the inked embossed portion presents an image that can supplement or be part of an image, for example, presented by a casting-curing structure.

[0188] Figure 36 Another example is illustrated, in which the safety device includes a casting-curing structure 80 and an inked imprinting portion 90 formed by an intaglio printing plate, wherein the intaglio element 91 is arranged only on top of the raised portion 81 of the casting-curing structure. It should be noted that the registration of the intaglio element 91 with the features of the casting-curing structure 80 (e.g., the intaglio element is positioned only within the recess or only on top of the casting element 81) is shown in one direction (parallel to the x-axis). However, such registration can also be in any direction relative to the casting structure 80, such as parallel to the z-axis.

[0189] Figure 37 Another example is shown in which the gravure element 91 is located both on top of the raised protrusions 81 of the casting-curing structure and within the recesses between the raised protrusions 81.

[0190] Figures 38(a) to 38(c) A further development of the invention is illustrated, wherein the casting-curing structure 80 includes a raised platform 81a, and a gravure article is applied to the raised platform. In FIG. 38(a), a gravure element 91 is applied on the raised platform 81a (region A) and in region B adjacent to the casting platform. In other words, the gravure element 91 in region B is formed directly on the surface 3a of the substrate 2. The gravure article in region B can be formed separately from the gravure article in region A; for example, the gravure article in region B can be provided before casting the raised platform 81a and subsequently providing the gravure element 91 in region A. However, preferably, the gravure elements in both regions A and B are applied in the same article, which advantageously allows the use of a single gravure printing plate or blanket to provide the gravure element 91 at different heights. FIG. 38(b) and FIG. 38(c) illustrate variations in which the casting-curing structure 80 includes a plurality of raised protrusions 81 (corresponding to elements of a halftone image) adjacent to the raised platform 81a. In Figure 38(b), the gravure element 91 is only provided on the raised platform, while in Figure 38(c), the gravure element is provided on both the raised platform 81a and the area of ​​the raised element 81.

[0191] Figure 39 and Figure 40 Another example is shown, in which the safety device includes a casting-curing structure 80 and an inked embossed portion 90 formed by a gravure printing plate. Figure 39 In this configuration, the gravure element 91 is arranged on top of the casting-curing structure 80 in a recess between the protrusions 81. Figure 40 In the example, the cast-to-cured structure defines at least one raised planar platform 81a and a gravure 90 is applied to the raised planar platform 81a and the adjacent base layer region 89. In this way, cast-to-cured can be used to improve the achievable height range of the component.

[0192] Figure 41 and Figure 42 An example of a safety device is illustrated, wherein the cast-cured structure is in the form of a surface relief structure 20, which includes the tactile structure 30 as described above. Figure 41 In the process, the cast surface relief structure 20 includes multiple raised protrusions 21, with the tactile structure 30 disposed only on the top of the raised protrusions. The gravure article 90 is aligned with the surface relief structure 20 such that the gravure element 91 is disposed only within the recess between the raised protrusions 21. Due to the size and shape differences between the gravure element 91 and the tactile structure 30 of the solidified surface relief structure, the authenticator will... Figure 41 When they move their fingers on the structure shown, they will experience a perceptible difference in tactile sensation.

[0193] The embossed structure can be applied to the substructure of the cast surface relief structure 20. Figure 42 An example is shown in which the cured surface embossed structure 20 includes a second-level set of embossed elements that defines a tactile structure 30-1 within a recess between raised elements 21, with an intaglio element 91 formed on top of the tactile structure 30-1. In other variations, an embossed element may be formed on a tactile structure 30-2, which is disposed on top of the first-level embossed elements 21 of the cast structure.

[0194] exist Figures 35(a) to 42 In each of the figures, the embossed structure is the inked embossed portion. Typically, the ink will have a visible color under certain viewing conditions (usually white light illumination). Especially in embodiments where the cast surface relief structure is also colored, this allows for the generation of complex color effects, such as providing colored images. In variations of these examples, gravure embossing can be blind embossing, i.e., without ink.

[0195] It is important to note that Figures 35(a) to 42 The embossing properties of the substrate that will appear in practice due to the gravure process (and are schematically shown in Figure 2(b)) are not illustrated. Preferably, in embodiments that include both casting and embossing structures, the cured resin of the casting structure is at least as flexible as the substrate (i.e., has the same or greater flexibility).

[0196] Figure 43 Further alternatives are depicted, in which the cast-solidified structure is configured to vary in height to follow the contours of a 3D image, such as a face (portrait), mountains, or other objects. Here, the surface relief structure 20 includes multiple substructures that help define the entire three-dimensional contour with a tactile feel.

[0197] Typically, the safety device 10 of the present invention can be disposed within a window area, a half-window area, or a non-window area (or a combination thereof) of the substrate, and... Figures 44(a) to 46(b) Some examples of possible configurations are shown in the figure. For simplicity, the surface relief structure is depicted only schematically.

[0198] exist Figures 44(a) to 44(e)In each of these, the substrate 2 is depicted as a multilayer substrate comprising a transparent core substrate 2a of a polymer (such as BOPP), wherein opaque layers 2b are disposed on each side of the transparent core substrate. Figure 44(a) depicts a safety device 10 disposed in a window region 51 of the substrate 2, i.e., where the two opaque layers 2b are absent in the window region 51, making the substrate partially transparent. The area of ​​the substrate 2 having a standard, basic level of opacity is referred to as the non-window region 50. In the example shown, this corresponds to the area where the two opaque layers 2b are uniformly present on both sides 3a, 3b of the substrate. In Figure 44(a), the window region 51 is surrounded by the non-window region 50. In these non-window regions, the substrate 2 has its highest level of opacity.

[0199] In Figure 44(b), the device 10 is located in a half-window 52, ​​i.e., one of the opaque layers 2b is absent while the other is present in the half-window 52. Therefore, the half-window region 52 is translucent rather than transparent and has a lower opacity than the surrounding non-window region 50. In this example, the half-window region 52 is formed by partially omitting the opaque layer 2b on the first surface 3a of the substrate, such that the surface relief structure is formed directly on the surface of the transparent core substrate 2a (optionally via a primer layer or other surface treatment). An inverted arrangement is shown in Figure 44(c), where the half-window is formed by retaining the opaque layer on the first surface 3a of the substrate and omitting the opaque layer from the second surface 3b.

[0200] Figure 44(d) illustrates a security device located within a non-window area 50 of the substrate 2. If desired, the non-window area can be opaque, in which case the optical effects presented by the surface embossed structure will be visible only under reflected light. In some embodiments, it may be desirable for the non-window area 50 containing the security device to have a sufficiently low level of opacity so that the security device 10 can be observed in transmitted light. Standard polymer banknote substrates and conventional paper banknote substrates typically meet this requirement.

[0201] Figure 44(e) schematically illustrates a more complex example, in which the same surface relief structure 20 is formed on different regions of the substrate 2. Here, the surface relief structure, in the form of a continuous block of cured material, comprises three laterally separated relief element regions (generally shown as A, B, and C), which are connected by a base layer 29. In this example, the relief element of region A is disposed in the half-window region 52; the relief element of region B is disposed in the window region 51; and the relief element of region C is disposed within the non-window region 50.

[0202] As mentioned, more than one opaque layer can be present on each side of the core substrate to provide the desired level of opacity.

[0203] In some embodiments, two or more surface embossed structures 20-1, 20-2 may be disposed on the opposite side of the security document substrate, such as... Figure 45 As shown. Here, two surface relief structures define separate safety devices, wherein surface relief structure 20-1 is disposed in window region 51 on the first surface 3a of the substrate, and surface relief structure 20-2 is disposed in non-window region 50 on the opposite surface 3b of the substrate.

[0204] In other embodiments, such as shown in FIG46(a), the security device 10 may be formed on a conventional document substrate 2. Such substrates are typically fibrous in nature, including, for example, paper or regenerated cellulose, as described in WO2020 / 156655.

[0205] In all embodiments described so far, as stated at the outset, it has been assumed that the security device is formed on substrate 2, which also serves as the document substrate for the final security document 100. Suitable document substrates include polymer document substrates of the types already mentioned above, wherein substrate 2 comprises a core substrate of a transparent polymer material such as polypropylene (PP) (most preferably biaxially oriented PP (BOPP)), polyethylene terephthalate (PET), polyethylene (PE), polycarbonate (PC), polyvinyl chloride (PVC), nylon, acrylic, cyclic olefin polymer (COP) or cyclic olefin copolymer (COC), or any combination thereof. The polymer substrate 2a may be monolithic, for example formed from a single material among the above materials, or may be multilayered, for example, multiple layers of the same type of polymer (optionally with different orientations) or layers of different polymer types. As previously mentioned, "transparent" means that the polymer substrate 2a is visually substantially transparent, but it may have a colored base color and / or another optically detectable material, such as a fluorescent material.

[0206] One or both surfaces of the polymer substrate 2a can be treated to improve the adhesion / retention of subsequently applied materials. For example, a primer layer can be applied to all or part of either surface of the polymer substrate 2a, for example, by printing or coating. The primer layer is preferably also transparent and can be recolored or have another optically detectable material. Suitable primer layers comprise compositions containing polyethyleneimine, hydroxyl-terminated polymers, hydroxyl-terminated polyester copolymers, crosslinked or uncrosslinked hydroxylated acrylates, polyurethanes, and UV-curable anionic or cationic acrylates.

[0207] Alternatively, or in addition to applying a primer layer, the surface of the polymer substrate 2a can be prepared for subsequent processing by controlling its surface energy. Suitable techniques for this purpose include plasma or corona treatment.

[0208] One or more opaque layers 2b each comprise an opaque material, the primary purpose of which is typically to provide a suitable background for subsequent printing of graphics. Therefore, preferably, the opaque layers comprise a polymeric non-fibrous material containing at least a light-scattering substance, such as pigment. The opaque layers 2b are preferably light-colored, most preferably white or another light color, such as off-white or gray, so that the later-applied graphic layer will contrast sharply with it. In a preferred example, each opaque layer has a luminance L* of at least 70, preferably at least 80, and more preferably at least 90 in the CIE L*a*b* color space. For example, each opaque layer may comprise: a resin, such as a polyurethane-based resin, a polyester-based resin, or an epoxy-based resin; and an opaque pigment, such as titanium dioxide (TiO2), silicon dioxide, zinc oxide, tin oxide, clay, or calcium carbonate.

[0209] Two or more opaque layers can be applied to each surface of the polymer substrate 2a to achieve the desired opacity. The optical density of each layer itself is typically around 0.2 to 0.5. Preferably, three or more layers are applied to each surface, stacked on top of each other.

[0210] In a preferred embodiment, at least one of the opaque layers (preferably one layer on each surface of the polymer substrate 2a) is made electrically conductive, for example, by adding conductive pigments thereto. This reduces the effect of static charge that may accumulate on the security document during processing.

[0211] Prior to manufacturing the security device 10 of this disclosure, the opaque layer 2b is preferably applied to the polymer substrate 2a using a printing process such as gravure printing. However, in other cases, the opaque layer may be coated onto the substrate or applied by offset printing, flexographic printing, planographic printing, or any other convenient method. Depending on the design of the security document, the opaque layer may be omitted across a gap on one or both surfaces of the polymer substrate to form a window area (which may be a full window, a half window, or a combination of both), as described above. This can be achieved by appropriately patterning the opaque layer during the application process. In an alternative construction, the opaque layer 2b may include a self-supporting preformed layer (optionally including orifices to later form the window), which is then laminated onto the polymer substrate 2a. In this case, the opaque layer may be a polymer or may be a fibrous structure, such as paper, thus making the security document a “hybrid” paper / polymer construction.

[0212] The safety device 10 can also be formed on a substrate other than the document substrate 2. For example, the safety device 10 can be formed on its own substrate to produce a safety article 1, such as a safety thread, strip, foil, or patch. The safety article can then be attached to or bonded to the safety document 100, for example by adhesive or via hot or cold pressing. An example is shown in Figure 46(b) in which the safety device 10 is formed on a secondary substrate 2' such as a transparent polymer film (e.g., PET). The secondary substrate 2' is typically thinner than the document substrate 2 (e.g., about 30 to 50 micrometers thick, rather than 100 micrometers or more). A surface relief structure 20 is formed on a first surface of the substrate 2'.

[0213] In this example, the security article 1 is shown attached to a first surface 3a of the security document substrate 2, wherein the security device 10 (or at least a portion thereof) is located above a window area 51 of the document, which is formed by an opening through the document substrate 2, which is typical in cases where the document substrate 2 is paper or the like. This security article 1 with the security device 10 can also be positioned in a non-window area 50 of the document substrate 2. The security article 1 can alternatively be applied to polymer-type document substrates in window areas, half-window areas, and / or non-window areas of the document substrate.

[0214] In another example, the second-level substrate 2' can be fixed to the document substrate 2, and then a surface relief structure 20 can be formed on top of the second-level substrate. The surface relief structure can be provided only on the second-level substrate 2', or on a combination of the second-level substrate (all or part) and the document substrate.

[0215] Suitable equipment, materials, and methods for forming the relief structures disclosed herein are described in WO-A-2018 / 153840 and WO-A-2017 / 009616. Specifically, the relief structures can be formed using the in-line casting apparatus (e.g., detailed in WO-A-2018 / 153840) Figure 4 The device (referred to as 80) is formed using an imprinting tool 85 with a suitably designed micro-optical structure, from which the desired relief structure shape can be cast. Similarly, Section 2.1 of WO-A-2017 / 009616 (e.g., its...) Figure 4 The casting-curing apparatus and method disclosed in (a) through (8) can also be used to form the relief structures of this disclosure by replacing the relief 225 on the casting tool 220 with a suitable relief capable of casting the desired shape. It should be noted in particular that although WO-A-2017 / 009616 describes the use of this apparatus to form a focusing element, the same apparatus can also be used to form any desired relief structure, including those contemplated herein, by appropriately reconfiguring the relief 225.

[0216] Regardless of the casting equipment used, one or more curable materials for casting the relief structure can be applied directly to a tool with the desired relief shape (e.g., applied to the imprinting tool 85 of WO-A-2018 / 153840 or the casting tool 220 of WO-A-2017 / 009616), or one or more curable materials can be applied directly to the substrate on which the relief structure is to be formed, and then brought into contact with the tool (e.g., by pressing the tool onto the deposited curable material). Both options are described in the aforementioned document. Preferably, the latter option is used and one or more curable materials are applied to the substrate by screen printing as detailed in WO-A-2018 / 153840, thereby forming the desired relief structure. If the former option is used, it should be noted that: between applying the curable material to it and bringing it into contact with the substrate, it is preferable not to wipe the relief on the surface of the casting tool, so that the base layer of the curable material remains connected to the protrusions (e.g., raised elements) of the relief structure together with the substrate (the height of the base layer will be much smaller than the protrusions).

[0217] Suitable curable materials are disclosed in Section 2.1 of WO-A-2017 / 009616. UV-curable materials are most preferred. Curing of one or more materials preferably occurs simultaneously with the casting tool contacting and abutting the curable material against the substrate.

[0218] In all the methods described above, the curable material forming the surface relief structure 20 can have a variety of different compositions. The curable material is preferably radiation-curable and may include a resin, which can typically be one of the following two types:

[0219] a) Free radical cured resins, which are typically unsaturated resins or monomers, prepolymers, oligomers, etc., containing, for example, vinyl or acrylate unsaturated bonds, and crosslinked by using a photoinitiator activated by the radiation source used (e.g., UV).

[0220] b) Cationic curable resins, wherein ring-opening is achieved using photoinitiators or catalysts (e.g., epoxy resin types), which generate ionic entities under the radiation source used (e.g., UV). Following ring-opening is intermolecular crosslinking.

[0221] The radiation used to influence curing is typically UV radiation, but can include electron beams, visible light, or even infrared or higher wavelength radiation, depending on the material, its absorbance, and the process used. Examples of suitable curable materials include UV-curable acrylic clear embossing varnishes, or those based on other compounds such as nitrocellulose. Suitable UV-curable varnishes are UVF-203 from Kingfisher Ink Limited or NOA61, a photopolymer from Norland Products, Inc., New Jersey.

[0222] Due to the nature of the casting-curing process, the resulting relief structure typically includes a base layer of material on top of the substrate, at which the relief protrusions connect. In many cases, this base layer is integral with the relief structure and is formed of the same one or more curable materials, resulting from the shape of the cast relief and / or the manner in which the curable material is imprinted between the substrate and the casting tool during processing. Examples of such base layers and their formation are disclosed in Figures 8(a) and 8(b) of WO-A-2017 / 009619. A base layer in the form of a pedestal layer applied in a previous step may also be provided (alternatively or additionally). (WO-A-2017 / 09620) Figures 8(a) to 12 (c) discloses an apparatus and method for providing such a base layer.

[0223] WO-A-2018 / 153840 and WO-A-2017 / 009616 also disclose printing stations that can be located downstream of the aforementioned casting equipment (but alternatively, upstream). Printing stations such as these are suitable for applying any printed elements mentioned herein to the same side of the substrate as the cast relief structure, or to the opposite side. The equipment disclosed in WO-A-2018 / 153840 allows for particularly high registration between such cast relief structures and printed elements.

[0224] Examples of suitable casting-curing processes for forming surface relief structures 20, 80 suitable for use in the safety devices disclosed herein will be described with reference to Figures 47(a) and 47(b), which schematically illustrate structure 20 only. The process is shown as being applied to a support layer 201 comprising a transparent or translucent film, which may be the aforementioned document substrate 2, or may be another substrate 2' attached to or incorporated into the document substrate, or subsequently applied to the document substrate 2. Figure 47(a) depicts the device from a side view, while Figure 47(b) shows the support layer in a perspective view, with the manufacturing equipment itself removed for clarity.

[0225] First, a curable material 205 is applied to the support layer 201 using an application module 210, which includes a patterned printing roller 211 that supplies the curable material from a doctor blade chamber 213 via an intermediate roller 212. For example, the illustrated component can form part of a screen printing system. Other printing techniques, such as offset printing, flexographic printing, lithographic printing, or inkjet printing, can also be used. Such printing processes are preferred because the curable material 205 can then be laid only in its selected area 202 on the support 201, the size, shape, and position of which can be selected by controlling the printing process, for example, by appropriately configuring the pattern on the roller 211. However, in other cases, such as when a surface relief structure is to be formed over the entire support 201, a full-coverage method can be used. The curable material 205 is applied to the support 201 in an uncured (or at least not fully cured) state and can therefore be a fluid or a formable solid.

[0226] The support 201 is then conveyed to the casting module 220, which includes a casting tool 221 in the form of a roller with a surface relief 225 defining the shape of the surface relief structure to be cast into the curable material 205. As each region 202 of the curable material 205 contacts the roller 221, the curable material 205 fills the corresponding region of the relief structure, thus forming the surface of the curable material into the shape defined by the relief. The roller 221 can be configured such that the relief structure 225 is only present in the region corresponding to the shape and position of the first region 202 of the curable material 205.

[0227] The correct surface relief structure has been formed, and the curable material 205 is cured by exposing it to appropriate curing energy (such as radiation R from source 222). This preferably occurs when the curable material comes into contact with the surface relief 225, but if the material is already sufficiently viscous, this can be done after separation. In the example shown, the material is irradiated through the support layer 201 (e.g., a paper substrate or polymer substrate that is sufficiently transparent to the curing radiation for curing to occur), but if the roller is formed of a suitable transparent material (such as quartz), the source 222 can alternatively be positioned above the support layer 201 (e.g., inside the roller 221). In an alternative embodiment, the curable material 205 can be applied directly to the casting tool 221 instead of to the substrate 201. This can be done in a full-pattern or pattern-by-pattern manner.

[0228] Figure 48This is a schematic cross-sectional view of a portion of an exemplary casting tool 221, showing the surface relief 225 in more detail. The surface relief 225 of the casting tool includes a plurality of grooves 121. The base 121a of each groove 121 includes a substructure 130, which includes a plurality of substructure elements 131. Thus, when the curable material 205 comes into contact with the surface relief 225 of the casting tool 221, a surface relief structure is formed in the curable material, the surface relief structure including a plurality of raised protrusions 21 having dimensions and shapes corresponding to the dimensions and shapes of the grooves 121, wherein each raised protrusion has a plurality of tactile protrusions 31 on its top, these tactile protrusions 31 having dimensions and shapes corresponding to the dimensions and shapes of the substructure elements 131 of the casting tool. Therefore, the depth of the substructure element 131 of the casting tool is typically between 2 μm and 75 μm, preferably between 2 μm and 25 μm, more preferably between 2 μm and 10 μm, and the width of the substructure element 131 is between 2 μm and 75 μm, preferably between 2 μm and 25 μm, more preferably between 2 μm and 10 μm. The depth of the groove 121 is preferably in the range of 20 μm to 200 μm, preferably in the range of 20 μm to 150 μm, more preferably in the range of 20 μm to 100 μm, and even more preferably in the range of 20 μm to 50 μm, and the width of the groove 121 is in the range of 20 μm to 8 mm, more preferably in the range of 30 μm to 3 mm, even more preferably in the range of 30 μm to 1 mm, and even more preferably in the range of 50 μm to 500 μm. The raised areas (“spaces”) between the grooves of the surface relief structure will correspond to the base layer of the final surface relief structure. These can form uniform areas of the base layer in the final surface relief structure (123-1), or alternatively, the casting tool 221 may include substructures formed by a plurality of substructure elements 131 (as shown in 123-2), such that the final surface relief structure of the cured material presents a tactile structure in the recesses between the first-level elements. Due to the nature of the casting-curing process, the surface relief structure 225 defined in the casting tool 221 will be precisely replicated in the final device.

[0229] Typically, in embodiments where the curable material is applied directly to the casting tool 221, the curable material is applied to substantially fill the groove 121, and a thin layer of the curable material is formed on the raised areas of the surface of the casting tool 221 (e.g., with...). Figure 48(129 is schematically shown in the diagram). After the casting process, the thin layer 129 of the curable material forms an integral base layer of the surface relief structure. In an alternative method, the curable material 205 can be applied to the casting tool, for example, by using a doctor blade or other removal device, to make it exist only within the groove 121, to remove layer 129. In such an example, the adhesive coating layer is then applied substantially to the entire surface of the die form 221, i.e., to the filled recessed areas of the groove and the raised areas between the recessed areas. The curable material of the adhesive coating may or may not have the same composition as the curable material 205 in the groove. In a particularly preferred embodiment, the adhesive coating composition can be selected to improve the adhesion between the curable material 205 and the support layer. The adhesive coating is applied by an adhesive coating application module. It is desirable to apply the adhesive coating in a continuous, homogeneous manner at the micron level, and therefore it is preferably applied in a metering manner via a combination of a mold and transfer rollers. The adhesive coating can be partially cured before the casting tool and the substrate come into contact.

[0230] Section 1 of WO-A-2017 / 009616 discloses suitable substrates on which the disclosed device can be formed, and Section 4 discloses apparatus / methods for applying an opaque layer to the substrate, including the formation of a window region. Preferably, the opaque layer is applied before forming the currently disclosed safety device on the substrate. For example, the sheet of the device provided to WO-A-2018 / 153840 may include the kind of polymer substrate disclosed in WO-A-2017 / 009616, which has provided one or more opaque layers. The safety device disclosed herein may be disposed in a window region defined by the opaque layer or in a non-window region.

[0231] Further exemplary embodiments of this disclosure are set forth in the following numbered clauses:

[0232] Clause 1: A safety device comprising:

[0233] A surface relief structure formed by curing material on a substantially flat substrate, the surface relief structure defining a first-level relief element set at a first scale and a second-level relief element set at a second scale, the second scale being smaller than the first scale, the first-level relief element set including a plurality of raised protrusions spaced apart by recesses, and the second-level relief element set disposed on top of the raised protrusions and / or disposed in the recesses.

[0234] Clause 2: The safety device according to Clause 1, wherein the second-level relief element set defines the tactile structure.

[0235] Clause 3: The safety device according to Clause 2, wherein the tactile level (roughness / smoothness) of the tactile structure is configured to vary across the entire relief structure, and the top of the protrusion in the first region preferably has a higher tactile level than the top of the protrusion in the second region of the device.

[0236] Clause 4: The safety device according to Clause 2 or 3, wherein the tactile structure on top of the protrusion has a higher level of tactile sensation than the tactile structure in the recess between the protrusions.

[0237] Clause 5: The safety device according to Clause 1, wherein the second-level relief element set defines an optical element, which is preferably a prism, a mirror, or a focusing element, such as a lens or a focusing mirror.

[0238] Clause 6: A method of manufacturing a safety device, the method comprising: forming a surface relief structure on a substantially flat substrate using a curable material and curing the material, wherein the surface relief structure is formed by:

[0239] A casting tool is provided, the casting tool having a relief structure defined in the surface of the casting tool, the relief structure corresponding to the surface relief structure;

[0240] The curable material is applied to the substrate or to the relief structure of the casting tool;

[0241] The substrate and the casting tool are brought together to form the curable material according to the relief structure, and the curable material is cured so that the surface relief structure formed by the cured material is retained on the substrate.

[0242] The surface relief structure defines a first-level relief element set at a first scale and a second-level relief element set at a second scale, the second scale being smaller than the first scale. The first-level relief element set includes a plurality of protruding portions separated by recesses, and the second-level relief element set is disposed on the top of the protruding portions and / or disposed in the recesses.

[0243] Clause 7: The method according to Clause 6 is configured to provide the safety device with any one of Clauses 1 to 5.

[0244] Clause 8: A safety device comprising: a surface relief structure formed on a substrate by a cured material; and an embossed structure on or adjacent to the cured material on the substrate.

[0245] Clause 9: The safety device according to Clause 8, wherein the surface relief structure formed by the cured material defines a plurality of raised elements, the plurality of raised elements being spaced apart by a recessed base layer and the raised portion of the embossed portion being located on the base layer.

[0246] Clause 10: The safety device according to Clause 8, wherein the surface relief structure formed by the cured material defines at least one platform and an adjacent base layer region, the platform being higher than the base layer region, and the raised portion of the embossed portion being located on the platform and / or the base layer region.

[0247] Clause 11: A method of manufacturing a safety device, wherein the method:

[0248] a) Forming a surface relief structure on a substrate using a curable material and curing the material, wherein the surface relief structure is formed by:

[0249] a1) Provide a casting tool having a relief structure defined in the surface of the relief structure, the relief structure corresponding to the surface relief structure;

[0250] a2) Applying the curable material to the substrate or to the relief structure of the casting tool;

[0251] a3) Positioning the substrate and the casting tool together to form the curable material according to the relief structure, and curing the curable material such that the surface relief structure formed by the cured material is retained on the substrate; and

[0252] b) Perform gravure printing on the substrate to form an inked or uninked embossed portion on the substrate, the embossed portion being located on or adjacent to the surface relief structure.

[0253] Clause 12: The method according to Clause 11, wherein the method is configured to provide the safety device with any one of Clauses 7 to 10.

[0254] Clause 13: A safety device comprising: a surface relief structure formed by a cured material on a substantially flat substrate, the surface relief structure following the outline of a three-dimensional image, the three-dimensional image preferably being a portrait.

Claims

1. A safety device, the safety device comprising: A surface relief structure, formed by one or more cured materials on a substantially flat substrate, defines a first-level relief element set at a first scale and a second-level relief element set at a second scale, the second scale being smaller than the first scale. The first-level relief element set includes a plurality of raised protrusions spaced apart by recesses, and the second-level relief element set is disposed on top of at least one of the raised protrusions and / or in at least one of the recesses, wherein... The security device presents an image, wherein the elements of the image are provided solely by the surface relief structure; and further wherein, The second-level set of embossed elements defines one or more tactile structures, wherein the tactile level of one or more of the tactile structures is configured to vary across the entire surface embossed structure according to the image.

2. The safety device according to claim 1, wherein, The top of the protruding portion in the first region of the device has a different tactile level than the top of the protruding portion in the second region of the device.

3. The safety device according to claim 1 or claim 2, wherein, The recess between the protrusions in the first region of the device has a different tactile level than the recess between the protrusions in the second region of the device.

4. The safety device according to any one of claims 1 to 3, wherein, The tactile structure on the top of the protrusion has a different level of tactile sensation than the tactile structure in the recess between the protrusions.

5. The safety device according to any one of claims 1 to 4, wherein, The tactile structure defines the tactile level based on at least one of the size, shape, orientation, and / or spacing of the second-level relief element set.

6. The safety device according to any one of claims 1 to 5, wherein, In at least one region of the surface relief structure, the size, shape, orientation, and / or spacing of the second-level relief element set are substantially consistent.

7. The safety device according to any one of claims 1 to 6, wherein, In at least one region of the surface relief structure, the second-level relief element set has a non-periodic arrangement.

8. The safety device according to any one of claims 1 to 7, wherein, In at least one region of the surface relief structure, the tactile structure has an asymmetrical arrangement, such that the tactile level in the first direction is different from the tactile level in the second direction.

9. The safety device according to any one of claims 1 to 8, wherein, The second-level relief element set is in the form of at least one of the following: multifaceted structure; curved structure; irregular structure.

10. The safety device according to claim 9, wherein, The multifaceted structure is a prism, cube, cone, or pyramid shape.

11. The safety device according to any one of claims 1 to 10, wherein, The second-level relief element set has a size that makes it indistinguishable to the naked eye.

12. The safety device according to any one of claims 1 to 11, wherein, The protrusion height of the second-level relief element set is between 2 µm and 75 µm.

13. The safety device according to claim 12, wherein, The protrusion height of the second-level relief element set is between 2 µm and 25 µm.

14. The safety device according to claim 12, wherein, The protrusion height of the second-level relief element set is between 2 µm and 10 µm.

15. The safety device according to any one of claims 1 to 14, wherein, The width of the second-level relief element set is between 2 µm and 75 µm.

16. The safety device according to claim 15, wherein, The width of the second-level relief element set is between 2 µm and 25 µm.

17. The safety device according to claim 15, wherein, The width of the second-level relief element set is between 2 µm and 10 µm.

18. The safety device according to any one of claims 1 to 17, wherein, The recesses between the protrusions include a base layer of one or more cured materials or another base layer of one or more cured materials, whereby the plurality of protrusions of the first-level relief element set are connected by the base layer, which has a lower height than the protrusions of the first-level relief element set.

19. The safety device according to claim 18, wherein, The base layer extends over the peripheral region surrounding the protruding portion.

20. The safety device according to claim 18 or claim 19, wherein, The height of the base layer varies throughout the surface relief structure.

21. The safety device according to any one of claims 1 to 20, wherein, The height and / or width of the raised protrusions of the first-level relief element set vary across the entire surface relief structure.

22. The safety device according to any one of claims 1 to 21, wherein, The top of the protruding projection and / or the top of the second-level relief element set have a substantially constant height across at least a portion of the surface relief structure.

23. The safety device according to any one of claims 1 to 22, wherein, The image is a halftone image.

24. The safety device according to claim 23, wherein, The element is a line element, a dot element, or a defining mark, and the mark is a letter, number, or currency symbol.

25. The safety device according to claim 23 or claim 24, wherein, At least one of the size, shape, orientation, spacing, and / or color density of the raised protrusions varies throughout the surface relief structure to present a multi-tone variation of the image.

26. The safety device according to any one of claims 23 to 25, wherein, The device includes a first region and a second region, both of which present substantially the same image, but the tactile structures in the first region and the second region have different tactile levels.

27. The safety device according to claim 26, wherein, The tactile levels of the tactile structures in the first region and the second region are different along the first direction.

28. The safety device according to any one of claims 23 to 25, wherein, The device includes a first region and a second region, which present different images, but the tactile structures in the first region and the second region are substantially the same.

29. The safety device according to any one of claims 1 to 28, wherein, The plurality of raised protrusions include raised platforms, and wherein the second-level relief element set is at least partially located on the raised platforms.

30. The safety device according to any one of claims 1 to 29, wherein, The one or more cured materials have a color that is visible to the naked eye under at least some observation conditions.

31. The safety device according to any one of claims 1 to 30, wherein, The one or more cured materials are at least translucent.

32. The safety device according to claim 31, wherein, The one or more cured materials include visible colorants.

33. The safety device according to any one of claims 1 to 32, wherein, At least one of the cured materials includes a machine-readable substance.

34. The safety device according to claim 33, wherein, The amount of machine-readable material present in each region of the surface relief structure varies with the height of the region relative to the substrate, thereby the detection signal also varies with the height of the surface relief structure.

35. The safety device according to any one of claims 1 to 34, further comprising a decorative layer formed on a first surface and / or a second surface of the substrate, wherein, The surface relief structure is at least partially superimposed on the decorative layer, such that the decorative layer and the surface relief structure can be observed in combination under at least some observation conditions.

36. A secure document, the secure document comprising a document substrate and a security device on the document substrate, the security device being the security device according to any one of claims 1 to 35, wherein, The document substrate can be used as the substrate of the security device or not.

37. The security document according to claim 36, wherein, The document substrate includes paper, polymer, cellulose, or a mixture thereof.

38. The security document according to claim 36 or 37, wherein, The security device is located at least partially in the window area or half-window area of ​​the document substrate, and the window area or half-window area has a lower light density compared to the surrounding area.

39. The security document according to claim 36 or 37, wherein, The security device is located at least partially in the non-window area of ​​the document substrate.

40. The security document according to any one of claims 36 to 39, wherein, The document substrate includes a core polymer substrate having at least one opaque layer disposed on one or both surfaces of the core polymer substrate, and optional gaps in one or more of the opaque layers forming window areas or half-window areas of the document substrate.

41. The security document according to any one of claims 36 to 40, wherein, The document substrate also includes an integral decorative mark, which is at least partially superimposed on the surface relief structure.

42. The security document according to any one of claims 36 to 41, wherein, The substrate of the safety device is fixed to or attached to the document substrate.

43. The security document according to claim 42, wherein, The substrate of the security device is fixed to or bonded to a transparent or semi-transparent area of ​​the document substrate.

44. The security document according to any one of claims 36 to 43, wherein, The security document can be any of the following: banknotes, passport, identification document, ID card, bank card, driver's license, visa, stamps, cheques, or certificate.

45. A safety article comprising a safety device according to any one of claims 1 to 35.

46. ​​The safety article according to claim 45, wherein, The safety items are safety wires, strips, inserts, foils, or patches.

47. A method of manufacturing a safety device, the method comprising: A surface relief structure is formed on a substantially flat substrate by one or more curable materials and said one or more materials are cured, wherein the surface relief structure is formed by: A casting tool is provided, the casting tool having a relief structure defined in the surface of the casting tool, the relief structure corresponding to the surface relief structure; Apply one or more curable materials to the substrate and / or to the relief structure of the casting tool; The substrate and the casting tool are brought together to form one or more curable materials according to the relief structure, and the one or more curable materials are cured so that the surface relief structure formed by the one or more cured materials is retained on the substrate. The surface relief structure defines a first-level relief element set at a first scale and a second-level relief element set at a second scale, the second scale being smaller than the first scale. The first-level relief element set includes a plurality of protruding portions spaced apart by recesses. The second-level relief element set is disposed on the top of at least one of the protruding portions and / or disposed in at least one of the recesses. The security device presents an image, wherein the elements of the image are provided solely by the surface relief structure; and further wherein, The second-level set of embossed elements defines one or more tactile structures, wherein the tactile level of one or more of the tactile structures is configured to vary across the entire surface embossed structure according to the image.

48. The method of claim 47, wherein the method is configured to provide the safety device with the feature of any one of claims 1 to 35.

49. The method according to any one of claims 47 to 48, wherein, One or more curable materials are applied to the relief structure of the casting tool to substantially completely fill the recesses of the relief structure defined in the surface of the casting tool, and a layer of one or more curable materials is formed on the facade of the relief structure.

50. The method according to any one of claims 47 to 49, wherein, The relief structure of the casting tool includes a plurality of grooves, the plurality of grooves being spaced apart by raised regions, the grooves corresponding to a first-level relief element set, and wherein at least one of the grooves has a base and / or at least one raised region in the raised regions between the grooves having a substructure corresponding to a second-level relief element set.

51. A method for creating a security document, the method comprising: Provide a document substrate, and form a security device on the document substrate according to any one of claims 47 to 50, or form a security device on a security device substrate fixed to the document substrate or integrated into the document substrate according to any one of claims 47 to 50; Alternatively, the safety device may be formed on the safety device substrate by the method according to any one of claims 47 to 50; Then, the safety device substrate is applied to the document substrate or the safety device substrate is bonded to the document substrate.

52. The method of claim 51, wherein the method is configured to provide the security document with any of the features of claims 36 to 44.

Images